SYN-4842: excluded file types client

[borisvalo]

Resolves SYN-4842

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Before the change?

• syntheticsclient/v2 had browser check model support for excludedFiles, but no client method to discover the API-owned excluded file types.
• makePublicAPICall printed full dumped requests to stdout after setting X-SF-TOKEN, which could expose API tokens in logs.

After the change?

• Added ExcludedFileTypesResponse.
• Added GetExcludedFileTypesV2() for GET /excluded_file_types, parsing the public excludedFileTypes response field.
• Added unit coverage for the excluded file types client method and parser.
• Removed stdout request dumping from makePublicAPICall.
• Preserved RequestDetails.RequestBody compatibility while redacting the client API key before storing request details.

Pull request checklist

• Acceptance Tests have been updated, run (make testacc), and pasted in this PR (for bug fixes / features) - N/A: client SDK unit-only change.
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Acceptance Test Output

N/A. This client SDK change is covered by unit tests.

ok  	github.com/splunk/syntheticsclient/v2/syntheticsclientv2	1.359s

Does this introduce a breaking change?

• Yes
• No