[Caideyipi]

Description

A pipe created from a root session receives an injected source.user-id=0. After ALTER PIPE ... MODIFY SOURCE changes its username and password to another account, merged attributes retain that root ID. Table permission checks can continue treating the pipe as root and transfer data before SELECT permission is granted.

Resolve user IDs from explicit source and write-back sink usernames during create, replace and modify operations. Password-only modifications preserve the existing user ID.

Correctly enforcing the new identity also exposes a TsFile retry defect: throwIfNoPrivilege() clears table names and tree schema metadata after each check. A denied table event then throws a null-pointer exception on retry and cannot recover after SELECT is granted. Retain this metadata until the event releases its resources, including when processing fails after a successful check.

Regression coverage includes attribute merging, explicit credentials, password-only updates, repeated denial, grant/retry, revoke/retry, and repeated realtime tree permission checks.

Validation

• Confirmed the new retry regression fails before the fix with the same tableNames null-pointer exception as the original CI logs.
• PipeTsFileInsertionEventTest, PipeAuthenticationIdentityTest and ShowCreateTaskTest: 15 tests passed.
• IoTDBPipePermissionIT#testSourcePermission: passed in 61 seconds with two HighPerformanceMode clusters (Ratis/Ratis/IoT, schema replication 3, data replication 2).
• Spotless, changed-file Checkstyle, DataNode Apache RAT and git diff --check passed.

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This PR has:

• been self-reviewed.
• added unit tests to cover the changed code paths.

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Key changed/added classes

• TableConfigTaskVisitor
• PipeAuthenticationIdentityTest
• PipeTsFileInsertionEvent
• PipeTsFileInsertionEventTest