[fix](jdbc) Map SQL Server user-defined alias types via JDBC DATA_TYPE

[arimu1]

What problem does this PR solve?

Issue Number: close #67793

Related PR: N/A

Problem Summary:

SQL Server JDBC catalog schema discovery maps columns using JdbcSQLServerClient.jdbcTypeToDoris(), which only matched built-in TYPE_NAME values. User-defined alias types created with CREATE TYPE ... FROM varchar expose a custom TYPE_NAME (for example customtexttype) while DATA_TYPE remains Types.VARCHAR, so Doris mapped them to UNSUPPORTED and blocked queries.

Release note

Fixed JDBC SQL Server external catalog mapping for user-defined alias types when JDBC reports a standard scalar DATA_TYPE.

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:

• Behavior changed:

  • No.
  • Yes. Unknown TYPE_NAME values now fall back to JDBC DATA_TYPE for standard scalar types (e.g. varchar aliases → STRING). CLR/special types still reported as unsupported binary codes remain unsupported.

• Does this need documentation?

  • No.
  • Yes.

Test plan

• cd fe && mvn test -pl fe-core -am -Dtest=JdbcSQLServerClientTest -Dsurefire.failIfNoSpecifiedTests=false -Ddoris.thrift.executable=/opt/homebrew/bin/thrift
• JDK 17, Maven 3.9+

Fixes #67793

[hello-stephen]

Thank you for your contribution to Apache Doris.
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1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
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