Add package for measuring aspnet startup time.

Refactors the solution into three projects:

Agoda.Builds.Metrics (existing project keeping the same functionality, but some common files have been moved out.)
Agoda.DevFeedback.AspNetStartup (adds a HostedService and Middleware to measure time from app configure to app started and first response).
Agoda.DevFeedback.Common (shared implementations for reading the Git context and publishing the dev feedback data).

agoda-com / dotnet-build-metrics