Because it requires full rebuild of the base library, it adds about
20% to the build time of the test suite. Between the fact that the
option is deprecated, and that Bazel has added the `BAZEL_TEST`
env var _years_ ago, nobody should be using it, and the chance
of breakage is tiny, the test is not worth its compile-time cost.

As with other Bazel env vars, it overrides the corresponding CLI
parameter if both are set.

Closes #3021
Closes #3024

This commit causes small (~5%) slowdown when processing strings
that consist mostly of escaped characters, but improves throughput
by about 100% for strings that consist mostly of characters that
do not need escaping.

This cherry-picks the source changes from PR made by @pkleymonov-qnx,
without including the build path changes that are irrelevant unless
we can add a QNX target to our CI.

Close #2953

This tells Catch2 to create an empty file at specified path before
the tests start, and delete it after the tests finish. This allows
callers to catch cases where the test binary silently exits before
finishing (e.g. via call to `exit(0)` inside the code under test),
by looking whether the file still exists.

Closes #3020

Forbid deducing reference types for m_predicate in FilterGenerator to prevent dangling references.
This is needed for out-of-line predicates to work correctly instead of undefined behavior or crashes.

---------

Co-authored-by: Tek Mate <mate.tek@evosoft.com>

As with the JSON writer, the old code was made to be simple and
for each char just decided whether it needs escaping, or should be
written as-is. The new code instead looks for characters that need
escaping and batches writes of characters that do not.

This provides 4-8x speedup (length dependent) for writing strings
that do not need escaping, and keeps roughly the same performance
for those that do need escaping.

The old code was exceedingly simple, as it went char-by-char and
decided whether to write it to the output stream as-is, or escaped.
This caused a _lot_ of stream writes of individual characters.

The new code instead looks for characters that need escaping, and
bulk-writes the non-escaped characters in between them. This leads
to about the same performance for strings that comprise of only
escaped characters, and 3-10x improvement for strings without any
escaping needed.

In practice, we should expect the former rather than the latter,
but this is still nice improvement.