wip feat(passkey): Add glean metrics for passkey registration and management

[vpomerleau]

DRAFT Needs to be rebased once the passkey management ui wiring is merged

Because

• We need interaction data to understand passkey adoption and failure modes

This pull request

• Defines 8 new account_pref.passkey_* events in fxa-ui-metrics.yaml
• Regenerates accountPref.ts via glean_parser
• Adds eventsMap entries and recordEventMetric switch cases
• Instruments UnitRowPasskey (create submit), PagePasskeyAdd (view/success/error/cancel), and PasskeySubRow (delete submit/confirm/success)
• passkey_add_error includes reason extra key (webauthn/server/mfa_expired)
• Adds Glean mock and assertions to component test files
• Adds ping submission tests for all 8 events in lib/glean/index.test.ts

Issue that this pull request solves

Closes: FXA-13418

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