PYTHON-6140 [v4.18] [Build Failure] TestBSON.test_encode_size_limit MemoryError on Windows

[blink1073]

PYTHON-6140

Backport of #3092

Changes in this PR

Skip TestBSON.test_encode_size_limit on hosts with less than 6GiB of total physical memory. The test needs ~4GiB of peak memory to encode a document that exceeds the BSON size limit, but on 4GB windows-64-vsMulti-small hosts the allocations fail with MemoryError before the expected ValueError is raised.

Test Plan

• Verified locally: test_encode_size_limit now skips on a 4GiB host.
• Win32 tests pass in CI.

Checklist

Checklist for Author

• Did you update the changelog (if necessary)? N/A
• Is there test coverage? — N/A
• Is any followup work tracked in a JIRA ticket? N/A

Checklist for Reviewer

• Does the title of the PR reference a JIRA Ticket?
• Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
• Is all relevant documentation (README or docstring) updated?