[fix](fe) Accept BLOB prepared statement parameters

[1fanwang]

What problem does this PR solve?

Issue Number: closes #67301

Related PR: N/A

Problem Summary:

MySQL Connector/ODBC sends wide-character prepared-statement values with MySQL's BLOB type code. Doris rejects the parameter before statement execution with AnalysisException: Unsupported MySQL type: BLOB.

All four protocol-equivalent BLOB types now use the existing length-encoded string decoder. The unit test covers Unicode text and verifies that decoding consumes only the parameter payload.

Release note

Prepared statements now accept string parameters sent with MySQL BLOB type codes.

Check List (For Author)

• Test
  • Unit Test

Raw test output

$ git restore --source=2689e0d7fdb111bf822cebc26d7d5765a563e276 -- \
    fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/literal/Literal.java
$ ./run-fe-ut.sh --run org.apache.doris.nereids.trees.expressions.LiteralTest#testMysqlBlobParameter
Unexpected exception thrown: org.apache.doris.nereids.exceptions.AnalysisException: Unsupported MySQL type: BLOB
Tests run: 1, Failures: 1, Errors: 0, Skipped: 0
BUILD FAILURE

$ git restore --source=HEAD -- \
    fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/literal/Literal.java
$ ./run-fe-ut.sh --run org.apache.doris.nereids.trees.expressions.LiteralTest#testMysqlBlobParameter
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

• Behavior changed:

  • Yes. Prepared statements accept length-encoded BLOB parameters as string literals.

• Does this need documentation?

  • No.

Check List (For Reviewer who merge this PR)

• Confirm the release note.
• Confirm the test case.
• Confirm documentation impact.
• Add a branch-pick label if needed.

[hello-stephen]

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1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
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4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?