Instead of redoing the whole line where path was found, only the
directory part of the path is removed, instead of removing all
of the line before the path starts.

This results in slight change in how junit and sonarqube approvals
come out, and significant change in how TeamCity reporter approvals
come out. This latter difference is the reason for the change,
as now the lines with `testFailed` and `testIgnored` messages
are not completely butchered.

* Remove from __future__ import print_function, because we
  no longer support Python2.
* Clean out unused parts of tools/scripts/scriptCommon.py
* Move appveyorMergeCoverageScript to Python3
* Update user reporting in *release scripts
* Cleanup module imports

This has two effects:
 1) This significantly improves the performance of ApprovalTests
    run in WSL, because running the massively multi-reporter
    test would cause lots of small and parallel writes across the
    WSL-Windows FS boundary, completely mudering performance.

 2) ApprovalTests can be run from multiple build dirs in parallel,
    as long as they do not fail. However, if they do fail,
    the multiple runs will still step on each other toes when
    writing the unapproved files for user.

Fixes #2458

This means that the CLI interface now uses the new key-value oriented
reporter spec, the common reporter base creates the colour implementation
based on the reporter-specific configuration, and it also stores the
custom configuration options for each reporter instance.

Closes #339 as it allows per-reporter forcing of ansi colour codes.

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