Add support for S3 Multi-Region Access Point (MRAP) URLs

[fedemengo]

Closes #556

Changes

• cloudpathlib/s3/s3path.py: added _MRAP_PATTERN regex and overridden bucket property on S3Path
• tests/mock_clients/mock_s3.py: removed bucket name check from head_object (the mock never routes by bucket, only by key)
• tests/test_s3_specific.py: added 3 tests covering bucket/key parsing, path manipulation, and end-to-end file operations via the
  mock backend

Note: using MRAP paths requires botocore[crt] for SigV4a signing:

pip install botocore[crt]

---

Contributor checklist:

• I have read and understood CONTRIBUTING.md
• Confirmed an issue exists for the PR, and the text Closes #issue appears in the PR summary (e.g., Closes #123).
• Confirmed PR is rebased onto the latest base
• Confirmed failure before change and success after change
• Any generic new functionality is replicated across cloud providers if necessary
• Tested manually against live server backend for at least one provider
• Added tests for any new functionality
• Linting passes locally
• Tests pass locally
• Updated HISTORY.md with the issue that is addressed and the PR you are submitting. If the top section is not `## UNRELEASED``, then you need to add a new section to the top of the document for your change.

[fedemengo]

the changes were simple enough, @pjbull gentle ping for review

[pjbull]

A couple comments.Also is it possible to update the tests to use s3_rig following the pattern of the existing tests rather than using S3Path directly (as in some tests) or using monkeypatch as in the others.

[pjbull]

Let's cache this since it shouldn't change.

[pjbull]

IIRC some of the tests use this check in some scenarios. Can we also just add a simple check that it doesn't have '.mrap' here

[fedemengo]

@pjbull I replaced S3Path with rig_ops when tests are not purly path parsing

[pjbull]

@fedemengo see linting errors in the action logs.

[fedemengo]

@fedemengo see linting errors in the action logs.

@pjbull I had missed that 8daee30

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.1%. Comparing base (5124aa0) to head (8daee30).

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #557     +/-   ##
========================================
- Coverage    94.0%   93.1%   -0.9%     
========================================
  Files          28      28             
  Lines        2203    2211      +8     
========================================
- Hits         2071    2060     -11     
- Misses        132     151     +19     

Files with missing lines	Coverage Δ
cloudpathlib/s3/s3path.py	100.0% <100.0%> (ø)

... and 3 files with indirect coverage changes

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[pjbull]

@fedemengo tests are failing on windows because : is not a valid character in the filepath.

We're coming up against this separate issue:
#439

Maybe for now you can override the _local property on S3Path and if there is a : and we are on Windows, we percent-encode the :?