fix(adapter/aws-lambda): APIGWProxyResult should contain either of headers or multiValueHeaders, not both

[exoego]

Closes #3870

• APIGWProxyResult now contains headers or multiValueHeaders mutually-exclusively.
• handle is tweaked so the response type can be inferred from the request event type.

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• Add TSDoc/JSDoc to document the code

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.28%. Comparing base (035c2d7) to head (ce60722).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3883      +/-   ##
==========================================
- Coverage   91.32%   91.28%   -0.04%     
==========================================
  Files         168      168              
  Lines       10687    10767      +80     
  Branches     3021     3091      +70     
==========================================
+ Hits         9760     9829      +69     
- Misses        926      937      +11     
  Partials        1        1              

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[rown89]

Hello, i have the same duplicate header issue, someone can take care of this PR and maybe merge ? :)

[yusukebe]

LGTM!

[yusukebe]

@exoego

Looks good to me! I'll merge now. Thank you!