We don't display the phases in the chart when missing some timings

See this profile: https://perfht.ml/30oH2HW

The first requests don't have the timings 'requestStart', 'responseStart', 'responseEnd', and as a result we don't display properly the phases in the row. The existing code was made by assuming we always had these timings, and this is clearly a wrong assumption here. So we'll need to find a better algorithm that can also handle these cases.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-154)

Open the linked performance profile and inspect the chart rows for the initial requests that lack requestStart, responseStart, and responseEnd. Trace the chart rendering entry point from that reproduction and determine how phases are currently derived. Done means rows display the available phases correctly even when those timings are missing.

Written by the indexing model from the issue text.