feat: add diagnostic logging for setter/selectPlacements timing

[alexs-mparticle]

Summary

• Logs each attribute/identity setter call (setUserAttribute, removeUserAttribute, onUserIdentified, onLoginComplete, onLogoutComplete, onModifyComplete) via LoggingService.logDiagnostic() with the affected attribute keys (never values).
• Logs each selectPlacements dispatch with the full set of placement attribute keys.
• The two log calls are independent — no in-kit correlation or timing math. The delta between "attributes set" and "placement requested" is computed downstream using the logged timestamp-of-receipt and page URL that ReportingTransport already attaches to every log request.
• logDiagnostic() ships at severity: "INFO" on the wire (same as log()) but under its own isolated rate-limit bucket, so a burst of setter/placement diagnostics can't starve the operational INFO budget shared with page-view/quota logging.
• Only attribute keys are ever logged — never values — since setter payloads can carry customer PII and this ships over the network logging pipeline.

Example log messages

Rokt Kit: setUserAttribute called [attributeKeys=favoriteColor]
Rokt Kit: onUserIdentified called [attributeKeys=email,firstName,loyaltyTier]
Rokt Kit: selectPlacements dispatched [placementAttributeKeys=email,firstName,loyaltyTier,mpid]

Test plan

• npm run lint passes
• npm run build passes (pre-existing IUserIdentities/getMPID type errors reproduce identically on main — unrelated to this change)
• npm run test — 340/340 passing, including new unit tests for diagnosticTiming.ts and integration coverage for every setter/identity call site and the selectPlacements dispatch

[alexs-mparticle]

Superseded — the rokt kit now lives in the mparticle-web-sdk monorepo under kits/rokt. Relanded here: mParticle/mparticle-web-sdk#1386