Add close() method to RestCatalog

[dingo4dev]

Part of #2399

Rationale for this change

This PR introducs the implementation of close() method to the RestCatalog.

And add corresponding test case which following the test pattern in #2390

Are these changes tested?

Yes

Are there any user-facing changes?

[Copilot]

Pull Request Overview

This PR adds a close() method to the RestCatalog class to properly close the HTTP session and release connection adapters. This implements proper resource cleanup for the REST catalog.

• Added the close() method implementation that calls self._session.close()
• Added comprehensive test coverage for the close functionality
• Included tests for both regular and SigV4-enabled catalog configurations
• Added context manager exception handling tests

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
pyiceberg/catalog/rest/init.py	Added the close() method implementation to RestCatalog class
tests/catalog/test_rest.py	Added comprehensive test suite for the new close functionality

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[kevinjqliu]

LGTM!