Removed:
* NaN normalization
* INFINITY normalization
* errno normalization
* Completely unused duration regex
Tests using these macros should be tagged `[approvals]`
so they are not run as part of approval tests.
Also simplified regex for the test's executable filename,
and hidden some tests relying on nullptr normalization.
This requires a bunch of different changes across the reporter
subsystem.
* We need to handle multiple reporters and their differing
preferences in `ListeningReporter`, e.g. what to do when
we mix reporters that capture and don't capture stdout.
* We need to change how the reporter is given output and
how we parse reporter's output destination from CLI.
* Approval tests need to handle multireporter option
