Performance metrics gathering

We should embed measurements into the code and send analytics to our side.
Metrics reporting must be optional and turned off by default in production build (see #77).

Metrics should cover various potentially long operations.
Reports should contain information about device used and parameters of operation called.

Start by reviewing issue #77 and the existing Kotlin/Android project structure; this issue names no files, entry points, or tests. Identify which potentially long operations and analytics destination are in scope, then define how reporting is disabled by default in production and what device and operation parameters reports include. Done requires an agreed scope and tests or verification for optional, production-off reporting.

Written by the indexing model from the issue text.