Add Latency Logs to Autofill Server

Test: manual build + manual test of logging, cts tests added later

This adds the following latency metrics:
1. fill_request_sent_timestamp_ms, set when frameworks requests a
   FillRequest from the autofill provider

2. fill_response_received_timestamp_ms, set when autofill provider provides a FillResponse

3. suggestion_sent_timestamp_ms, set when framework sends the FillResponse suggestions to be displayed

4. suggestion_presented_timestamp_ms, set when the suggestions are actually displayed

Fixes: 243719509

Change-Id: I577266b1b2bbdc53663c4707b5c9578f0c0e14ca
Merged-In: I577266b1b2bbdc53663c4707b5c9578f0c0e14ca