Fix bugs in Cirq converter and refactor

[purva-thakre]

Description

Noticed the bug/missing gates while working on unitaryfoundation/mitiq#3094

Related Issues

Closes #
Related to #

Type of Change

• Feature (new functionality)
• Change Request (modification of existing functionality)
• Bug Fix
• Refactoring (no behavior change)
• Performance improvement
• Documentation
• CI / Build

Breaking Change?

• Yes
• No

If yes, describe the impact and migration path:

What was changed?

How was it tested?

Test-ID	Status
T-001	✅ / ❌
T-002	✅ / ❌
T-003	✅ / ❌
T-004	✅ / ❌

Screenshots / Output (if applicable)

Checklist

• My code follows the project's coding standards
• I have performed a self-review
• I have added/updated tests (referencing issue Test-IDs)
• All tests pass locally and in CI
• I have updated the documentation
• I have added a changelog entry to changelog-dev.rst
• Breaking changes are documented with migration path

Reviewer Notes