feat: more mutation test cases for immutable detector

[taasbaba]

Description

This PR extends the ImmutableAccountMutatedDetector to cover more mutation patterns that can slip past the current checks, and adds a couple of negative tests to make sure it doesn’t false positive.

Key changes

1. Added detection for:

   • Two-level dereference with a chained call to try_borrow_mut_lamports()
   • Same as above but with extra parentheses and to_account_info() variant
   • Lamports modification on an UncheckedAccount
   • Calling a method that takes &mut self on an immutable account

2. Test updates:

   • Added tests for all the above new cases.
   • Added two negative tests to verify no false positives:
     • Local shadow variable (normal struct, not an account)
     • Sysvar, Program, and Signer accounts
   • Added a test for directly replacing an entire account struct — turns out the current detector already catches this, so this was just to confirm.

Verification

• Ran all tests locally — everything passes.
• Checked in Extension Development Host — new patterns are flagged as expected, negative tests pass.

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Related Tickets & Documents

• Closes Add detection for extra immutable account mutation patterns #25

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• I clicked on "Allow edits from maintainers"