The thread-safety changes in assertions & messages turned whether
the last assertion passed or failed into thread-local state,
instead of being member of the `RunContext`. However, this change
was not reflected in the API `CHECKED_IF`/`CHECKED_ELSE` used,
which in turn required `catch_test_macro_impl.hpp` to include
`catch_interfaces_capture.hpp` for it.

Thanks to the combination of this commit and the previous similar
commit for the message stack handling, the main include path does
not need to include `catch_interfaces_capture.hpp` anymore.

Since the change to make the message macros thread-safe, and thus
thread-local, there is no need to handle messages through instance
of `RunContext`.

Together with the previous change, this means that `ScopedMessage`
only needs to keep around a single unsigned int.

This builds on the existing work to make assertion thread safe,
by adding an extra synchronization point in the holder of
`ReusableStringStream`'s stream instances, as those are used to
build the messages, and finishing the move of message scope holders
to be thread-local.

All the previous refactoring to make the assertion fast paths
smaller and faster also allows us to implement the fast paths
just with thread-local and atomic variables, without full mutexes.

However, the performance overhead of thread-safe assertions is
still significant for single threaded usage:

|  slowdown |  Debug  | Release |
|-----------|--------:|--------:|
| fast path |   1.04x |   1.43x |
| slow path |   1.16x |   1.22x |

Thus, we don't make the assertions thread-safe by default, and instead
provide a build-time configuration option that the users can set to get
thread-safe assertions.

This commit is functional, but it still needs some follow-up work:
 * We do not need full seq_cst increments for the atomic counters,
   and using weaker ones can be faster.
 * We brute-force updating the reporter-friendly totals from internal
   atomic counters by doing it everywhere. We should properly trace
   where this is needed instead.
 * Message macros (`INFO`, `UNSCOPED_INFO`, `CAPTURE`, etc) are not
   made thread safe in this commit, but they can be made thread safe
   in the future, by building on top of this work.
 * Add more tests, including with thread-sanitizer, and compiled
   examples to the repository. Right now, these changes have been
   compiled with tsan manually, but these tests are not added to CI.

Closes #2948

This improves the fast path performance for successful assertions
by about 7%, at the cost of potentially keeping around the message
allocation longer.

This costs us about 1% perf in Debug build and 3% in Release build,
but it is worth it for more precise information during unexpected
exceptions or fatal errors.

Given a simple test case like this
```cpp
TEST_CASE("Hard fail") {
    REQUIRE( 1 == 1 );
    REQUIRE( 2 == 2 );
    throw 1;
    REQUIRE( 3 == 3 );
}
```

Catch2 before this change would report the line info from the
`TEST_CASE` macro as the last seen expression before error. With
this change, it will correctly report the line info from the
`REQUIRE(2 == 2)` assertion as the last seen expression before error.

As it is an internal helper for RunContext to speed-up handling of
succesfull assertions, I have no idea why it was added to the
interface back when it was first implemented.