feat: add metaMetricsIds explicit targeting to threshold feature flags

[pedronfigueiredo]

Summary

• Adds optional metaMetricsIds?: string[] field to FeatureFlagScopeValue in the remote feature flag controller types
• When the current user's MetaMetrics ID matches an entry's metaMetricsIds list, that entry is selected immediately, bypassing hash-based rollout
• Explicit-ID matches bypass the threshold cache; hash-based fallback continues to use and populate the cache as before
• metaMetricsIds values are redacted from rawRemoteFeatureFlags before persisting to state, so they never appear in state logs or debug snapshots
• Local overrides still take precedence over explicit-ID targeting

Behaviour

• IDs are compared case-insensitively after trimming whitespace
• First matching entry wins when multiple entries share the same ID
• Entries with malformed metaMetricsIds (non-array) are silently skipped; those entries still participate in hash-based selection
• Intended for QA and Product Manager testing in any environment, not general-purpose segmentation

Test plan

• All existing tests pass (66 total)
• New metaMetricsIds explicit targeting describe block covers: exact match, first-match-wins, hash fallback, malformed entries, non-string items, normalization, cache bypass, cache fallback population, state redaction, and ThresholdVersion.DirectValue compatibility

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Note

Medium Risk
Changes core threshold selection and persists redacted flag payloads; misconfigured remote metaMetricsIds could steer specific users in production, though hash rollout and local overrides behavior remain.

Overview
Adds optional metaMetricsIds on threshold flag entries so QA/PM users can be pinned to a variant before hash-based rollout runs.

Threshold processing now checks findExplicitIdMatch first (trim + case-insensitive ID compare, first matching entry wins, malformed lists skipped); on match it resolves the entry’s value and optional group name without writing thresholdCache. Otherwise behavior is unchanged: hash threshold + cache.

redactMetaMetricsIds strips targeting lists from rawRemoteFeatureFlags and processed remoteFeatureFlags before state persistence so IDs do not appear in logs or debug snapshots. Types and changelog are updated; a large test suite covers match, fallback, cache, redaction, and ThresholdVersion.DirectValue.

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