Add checkstyle rules fit for v2

[RanVaknin]

mapper v2 "house cleaning" PR

dynamodb-mapper (mapper v2) is a faithful 1:1 port of the EOL v1 DynamoDBMapper. Enabling the full v2 checkstyle ruleset would rename public types, change signatures, reorder members, and add code absent from v1. That turns the port into a refactor which is harder to diff against v1, and poses a behavior change risk.

This PR is "house cleaning", it makes sure the mapper module adheres to the v2 style and release requirement every module adheres to (where possible).

I did my best to break down the PR into independent commits by subject. Every subject is listed as a mechanical or low discretion change:

Changes Breakdown:

1. Static analysis suppressions + SDK annotations (mechanical, some discretion)

A faithful port trips three static analysis gates. Rather than adopting the full v2 rulesets, we suppress narrowly:

• Checkstyle: instead of the full ruleset we allowlist 3 rules:
  • HideUtilityClassConstructor (5): added private constructors to utility classes. Mechanical.
  • UnnecessaryFinalOnLocalVariable (216): removed unnecessary final on locals across 17 files. Mechanical.
  • MissingSdkAnnotation (110): added SDK API annotations. Discretion: classification follows the Enhanced Client convention.
    • 40 public visibility types → @SdkPublicApi
    • 68 marshaller/unmarshaller converters + 2 package private helpers → @SdkInternalApi
    • No @SdkProtectedApi
• Spotbugs (build-tools/.../spotbugs-suppressions.xml): 15 bug patterns carried over verbatim from v1, scoped to mapper.dynamodb.*, suppressed to keep the port byte-faithful rather than refactoring. Mechanical.
• ArchUnit (test/architecture-tests): 3 mapper classes added to the shouldNotAbuseWarnLog allowlist; DynamoDBMapperModelFactory, UpdateExpressionGenerator, and VersionAttributeConditionExpressionGenerator moved to internal/ to satisfy PackageContainmentTest. Mechanical.

Cross module note: this PR edits two shared files outside dynamodb-mapper: build-tools spotbugs-suppressions.xml, and archtests/ArchUtils.java (new classWithInnerClassesToPattern(String) helper, needed to allowlist an inner class warn by name without the arch tests module depending on the mapper).

2. Repo layout (mechanical)

Moved marshallers/unmarshallers/utils under internal/; moved true integ tests to src/it/. This is just package relative moves, no code changes.

3. Swap remaining v1 imports + logging (mechanical)

Remaining v1 SDK imports → v2 equivalents; commons-logging → SLF4J.

4. Remove dead code (mechanical)

Deleted unused DynamoDBReflector/ReflectionUtils; removed deprecated RequestMetricCollector from config (no v2 equivalent).

5. Restore data plane functional tests (mechanical)

Un excluded the DynamoDB Local functional tests that only use table admin for fixture setup (they actually test data plane operations) Pure table admin and S3Link tests stay excluded pending their ports.

6. Replace log4j 1.x with log4j2 (mechanical)

Swapped the log4j 1.x test dep for the SDK standard log4j-api/log4j-core/log4j-slf4j-impl (bom managed); replaced log4j.properties with log4j2.xml.

7. Build metadata (mechanical)

Declared the module's previously transitive v2 dependencies explicitly (sdk-core, aws-core, http-client-spi, auth, regions, annotations, utils). added the mapper to the .brazil.json mapping exclusion list.

Not in this PR (deferred to dedicated port PRs)

Table-admin/GSI port, S3Link port, and the v1 coupled tests they block.

---

**DDB mapper v2 roadmap: **

** BASE PACKAGE SETUP **
+ 1. Source verbatim port ✅
+ 2. Test verbatim port ✅
+ 3. Namespace swap (main + datamodeling tests) ✅ 
+ 4. Namespace swap (remaining test packages) ✅

** PORTING OPERATIONS **
+ 0. converters (AttributeValue seam) ✅ 
+ 1. load() ✅
+ 2. save() ✅
+ 3. query() + scan() ✅
+ 4. deleteItem() ✅
+ 5. updateItem() ✅
+ 6. Batch operations ✅
+ 7. Transactions ✅
8. S3Link
9. Table Admin (control plane convenience methods) 
- 10. Cleanup: <--- current PR

** PERFORMANCE IMPROVEMENTS **
1. getTableModel caching
2. Wire "fast" createX AV factory methods to convertors
3. ByteBuffer → SdkBytes copy
4. Others

** DEPENDENCY MODERNIZATION **
+ 1. EasyMock -> Mockito ✅
- 2. Log4j 1.x -> 2.x  <--- current PR
- 3. commons-logging -> SLF4J  <--- current PR

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[RanVaknin]

Appendix: full annotation classification

@SdkPublicApi: 40 public-visibility types

Core mapper (7)
DynamoDBMapper, AbstractDynamoDBMapper, IDynamoDBMapper, DynamoDBMapperConfig,
DynamoDBTableMapper, DynamoDBMapperTableModel, DynamoDBMapperFieldModel

Operation expressions / requests (9)
DynamoDBQueryExpression, DynamoDBScanExpression, DynamoDBSaveExpression, DynamoDBDeleteExpression,
DynamoDBTransactionLoadExpression, DynamoDBTransactionWriteExpression,
TransactionLoadRequest, TransactionWriteRequest, BatchLoadContext

Result / pagination types (6)
PaginatedList, PaginatedQueryList, PaginatedScanList, PaginatedParallelScanList,
QueryResultPage, ScanResultPage

Conversion & extension SPIs (10)
DynamoDBTypeConverter, DynamoDBTypeConverterFactory, ConversionSchema, ConversionSchemas,
ItemConverter, DynamoDBAutoGenerator, AttributeTransformer, AttributeTransformerChain,
ArgumentMarshaller, ArgumentUnmarshaller

S3 / misc (4)
S3Link, S3ClientCache, KeyPair, DynamoDBMappingException

Deprecated but public (4)
DynamoDBMarshaller, AbstractEnumMarshaller, JsonMarshaller, ParallelScanTask

@SdkInternalApi: 70 types

• marshallers/*: 23 converter classes (Java type → AttributeValue)
• unmarshallers/*: 45 converter classes (AttributeValue → Java type)
• MapperExceptions: internal exception helper