fix: match SourceMembers when server strips entity suffix @W-21612413@

[WillieRuemmele]

Summary

• Fix source tracking timeout after deploying platform events, big objects, external objects, or custom metadata types
• The SourceMember table may store child members without the entity suffix (e.g., MyEvent.Field__c instead of MyEvent__e.Field__c), causing the polling loop to never find a match and time out
• Adds suffix-fallback matching (__e, __b, __x, __mdt) in the polling loop when direct key lookup fails

Fixes forcedotcom/cli#3512

Work Item

@W-21612413@: Source tracking fails to update after deploy

Proof of Work

• Tests: 111 passing, 0 failing
• Lint: clean
• Type check: clean

Validation

• Per-task review: 4 findings (0 blocker, 1 medium, 3 low — all addressed or documented)
• Integration: all checks pass

Test plan

• Deploy a platform event with a custom field to a scratch org and verify source tracking completes without timeout
• Deploy a custom metadata type with fields and verify no timeout
• Deploy standard custom objects (with __c) and verify no regression in polling behavior
• Verify the Polling for N SourceMembers timed out warning no longer appears for platform event deploys