fix(signature-v4-multi-region): report available sigv4a dependency

[kuhe]

Codegen change

if (SignatureV4MultiRegion.sigv4aDependency() === "none" && sigv4Present) {
          // sigv4a -> sigv4 fallback.
          continue;
        }
.
.

Testing

• Unit

 ✓ src/SignatureV4MultiRegion.spec.ts (15)
   ✓ SignatureV4MultiRegion (15)
     ✓ sigv4aDependency (4)
       ✓ should return 'crt' when CrtSignerV4 is available
       ✓ should return 'crt' when CrtSignerV4 and SignatureV4a are available
       ✓ should return 'js' when only SignatureV4a is available
       ✓ should return 'none' when neither implementation is available
     ✓ should sign with SigV4 signer
     ✓ should presign with SigV4 signer
     ✓ should presign with SigV4 signer
     ✓ should sign with SigV4a signer if signingRegion is '*'
     ✓ should use SignatureV4a if CrtSignerV4 is not available
     ✓ should throw an error for presignWithCredentials with star region
     ✓ should throw when presigning with signingRegion '*' if CRT is NOT available
     ✓ should throw when presigning with signingRegion '*' in non-node runtime (CRT unavailable)
     ✓ should throw an error if neither CrtSignerV4 nor JsSigV4aSigner is available in node runtime
     ✓ should throw an error if JsSigV4aSigner is not available in non-node runtime
     ✓ should use JsSigV4aSigner in non-node runtime

 Test Files  1 passed (1)
      Tests  15 passed (15)
   Start at  15:41:01
   Duration  497ms (transform 110ms, setup 0ms, collect 231ms, tests 18ms, environment 0ms, prepare 81ms)

• Browser Unit

 ✓ src/SignatureV4MultiRegion.browser.spec.ts (3)
   ✓ SignatureV4MultiRegion (Browser Bundle SigV4a Test) (3)
     ✓ should use SigV4a for the request when signingRegion is '*' (JS implementation is available in bundle)
     ✓ should throw error when signingRegion is '*' and JS implementation is NOT available (Covered in Unit Tests)
     ✓ should correctly identify JS SigV4a implementation in browser environment

 Test Files  1 passed (1)
      Tests  3 passed (3)
   Start at  16:11:59
   Duration  1.09s (transform 252ms, setup 0ms, collect 302ms, tests 105ms, environment 373ms, prepare 72ms)

• E2E

 ✓ src/cloudfront-kvs-sigv4a.e2e.spec.ts (2) 395ms
 ✓ src/eventbridge-sigv4a-put-api.e2e.spec.ts (2) 1095ms

 Test Files  2 passed (2)
      Tests  4 passed (4)
   Start at  16:10:00
   Duration  1.91s (transform 502ms, setup 0ms, collect 1.09s, tests 1.49s, environment 0ms, prepare 183ms)