fix: fix several issues about the public schema

[yezizp2012]

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What's changed and what's your intention?

1. ensure the commands "show objects" and "show create object" function correctly within search_path, rather than use public schema by default.
2. make the public schema also managed by grant and revoke commands, which means that when creating a new non-super user, it is necessary to explicitly grant them the privilege of the public schema, which is also the default behavior of pg.

Checklist

• I have written necessary rustdoc comments.
• I have added necessary unit tests and integration tests.
• I have added test labels as necessary.
• I have added fuzzing tests or opened an issue to track them.
• My PR contains breaking changes.
• My PR changes performance-critical code, so I will run (micro) benchmarks and present the results.
• My PR contains critical fixes that are necessary to be merged into the latest release.

Documentation

• My PR needs documentation updates.

Release note

[gru-agent]

TestGru: The source file has been modified. Please add a comment @gru-agent under the changed file to notify the TestGru to rewrite the test code.