[INS-469] Added Rev detectors to defaults.go and gated it behind feature flag

[MuneebUllahKhan222]

Description:

This PR adds the existing Rev detector to defaults.go and ensures it is gated behind the appropriate feature flag.

Additionally, the PR updates the assertions in the existing integration tests to account for the changes made to the detector.Result struct.

Corpora Test:

The detector doesn't appear in the list.

Checklist:

• Tests passing (make test-community)?
• Lint passing (make lint this requires golangci-lint)?

---

Note

Medium Risk
Turning on a new default detector can change scan findings and verification traffic; rollout is mitigated by the same feature-flag pattern as other recently enabled detectors.

Overview
Enables the existing Rev (transcription API) detector in the default engine by registering rev.Scanner in buildDetectorList(), wiring RevDetectorEnabled in pkg/feature, turning it on in OSS main.go with the other gated detectors, and filtering the scanner out when the flag is off.

The Rev detector now populates SecretParts with both key and client (multi-part credential). Integration tests were updated to compare results with go-cmp, ignoring newer detectors.Result fields. defaults_test moves DetectorType_Rev from the “never added” exclude list into the feature-flag-gated group. go.mod drops two unused indirect modules after tidy.

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[github-actions]

Corpora Test Results

No detector regex or keyword changes in this PR. Bench skipped.

[cursor]

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