Remove SAM translator dependency, validate SAM templates via schemas

[kddejong]

Summary

Replace the aws-sam-translator runtime dependency with direct JSON Schema validation of SAM resource types. SAM templates are now validated against schemas from the enhanced schemas service, using the same provider schema infrastructure as CloudFormation resources.

Changes

• Remove _sam.py transform module and aws-sam-translator dependency
• Add _sam_globals.py to merge Globals section properties into SAM resources
• E3724: Validates Globals section structure against the SAM Globals schema
• E3066: Validates that Connectors and IgnoreGlobals require the SAM transform
• Lambda rule keywords: Extended Lambda rules (E2531, E2533, etc.) to also match AWS::Serverless::Function paths
• Sub-resource wildcard: SAM resources use the same module wildcard mechanism for Ref/GetAtt
• Implicit resource injection: SAM-generated resources (roles, versions, aliases, stages, permissions, etc.) are injected for validation
• GetAtt resilience: Handle unresolvable schema pointers gracefully instead of crashing

Behavioral Notes

• Input validation: SAM resource properties, Globals, events, and policies are validated against SAM schemas from the enhanced schemas service
• Output validation: We no longer validate the transformed CFN output (generated IAM roles, API Gateway stages, etc.). SAM owns that correctness
• Sub-resources: !Ref MyFunctionRole and !GetAtt MyFunction.Arn pass via the wildcard mechanism

Testing

• Unit tests for globals merging, implicit resource injection, and new rules
• Integration tests for good/bad SAM templates, IgnoreGlobals interaction
• All existing integration tests pass
• Verified no false positives on real-world SAM templates

Fixes #4556

[codecov]

Codecov Report

❌ Patch coverage is 98.85714% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.39%. Comparing base (cde01ee) to head (5e771ed).

Files with missing lines	Patch %	Lines
src/cfnlint/rules/functions/GetAtt.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4491      +/-   ##
==========================================
- Coverage   94.42%   94.39%   -0.04%     
==========================================
  Files         429      431       +2     
  Lines       15097    15121      +24     
  Branches     2915     2923       +8     
==========================================
+ Hits        14256    14273      +17     
- Misses        461      465       +4     
- Partials      380      383       +3     

Flag	Coverage Δ
unittests	94.39% <98.85%> (-0.04%)	⬇️

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