Test case hashing includes tags and class name
As the hasher involves more code now, it was split out into its own file
and it got its own set of tests.
Closes#2304
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
