Preserve private property scopes and add advice property accessors

[WalterWoshid]

Weaving previously made private properties public. A parent and child with independent same-name properties could then fail with incompatible types or silently share values. This preserves private declaring scopes and removes duplicate property promotion from generated forwarding constructors.

Adds $invocation->properties() for reads, writes, array mutation, references, isset/unset, and static property access. Pass the original declaring class when a name is ambiguous, for example $invocation->properties(ArgvInput::class)->tokens. The accessor operates on the actual subject and does not replace it or alter method interception.

Compatibility: advice accessing private properties directly must migrate to the accessor. PROPERTY_ACCESS.md documents the migration, cache regeneration, ambiguity rules, and native unset behavior. The database-modifier advice example is migrated.

Fixes #6.

Validation:

• 80 functional/integration tests pass locally on PHP 8.1–8.5 (22 new regression cases). Existing incomplete tests, PHP 8.1 readonly-class skip, and dependency deprecations remain.
• Independent code review completed; identified edge cases have regression coverage.
• Origin functional matrix passed: https://github.com/WalterWoshid/php-aop/actions/runs/33977166078
• Origin tracing-JIT performance matrix: https://github.com/WalterWoshid/php-aop/actions/runs/33977163887