This means that:
1) Scoped messages are always removed at the end of their scope,
   even if the scope ended due to an exception.
2) Scoped messages outlive section end, if that section's scope is
   enclosed in their own.

Previously neither of these were true, which has led to a number
of surprising behaviour, where e.g. this:
```cpp
TEST_CASE() {
    try {
        INFO( "some info" );
        throw std::runtime_error( "ex" );
    } catch (std::exception const&) {}

    REQUIRE( false );
}
```
would print "some info" as the message for the assertion, while this:
```cpp
TEST_CASE() {
    INFO("Hello");
    SECTION("dummy") {}
    REQUIRE(false);
}
```
would not print out "Hello" as the message for the assertion.

This had an underlying reason, in that it was trying to helpfully
keep the messages around in case of unexpected exceptions, so that
code like this:
```cpp
TEST_CASE() {
    auto [input, expected] = GENERATE(...);
    CAPTURE(input);
    auto result = transform(input); // throws
    REQUIRE(result == expected);
}
```
would report the value of `input` when `transform` throws. However,
it was surprising in practice and was causing various issues around
handling of messages in other cases.

Closes #1759
Closes #2019
Closes #2959

The fast path allows `RunContext` to skip disabling output redirect,
and notifying the reporters, turning `RunContext::notifyAssertionStarted`
into a no-op. This improves the overall performance of assertion handling
significantly, and also prepares ground for future changes around
assertion handling and thread safety.

For simple 10M assertion run, this improves the running time by ~30%
in Debug build and ~40% in Release build.

For backwards-compatibility reasons, the fast path is disabled
by default. However, none of the first party reporters use the
`assertionStarting` event, so all first party reporters are opted-in.

There were only two places where we used the full `AssertionInfo`
instance in `m_lastAssertionInfo`:
1) when reporting unexpected exception from running a test case
2) when reporting fatal error

because in those two places we do not have access to a real
instance of `AssertionInfo`, but we still need to send one to the
reporters. As a bonus, in both of these places we were already
constructing a fake-ish assertion info, by using the last encountered
source location, but dummying out the other information.

Instead, we only keep track of the last encountered source location,
and construct the dummy `AssertionInfo` on-demand.

This finishes the set of refactoring around `m_lastAssertionInfo`
in `RunContext` and improves the performance of running assertions
by ~5% in both Debug and Release mode.

--------------

Note that this change also causes small difference in output. It
could be avoided by having an invalidation flag and tracking where
the information would be invalidated before, but the difference
includes more precise line location for unexpected errors (both
exceptions and fatals), so I prefer the new output.

Closes #2582

Right now `TEMPLATE_TEST_CASE_SIG` fails to compile when the signature contains only types:

```
TEMPLATE_TEST_CASE_SIG(
  "TemplateTestSig: compiles with two type parameters",
  "[template][onlytypes]",
  ((typename U, typename V), U, V), (int,int)) {}
```

The trick is to resolve the ambiguity between the two overloads of
`get_wrapper` (`TypeList` and `Nttp`) by making one match more strongly.
We also need to allow `reg_test` to register more than one type.

Add unit tests.

Fixes #2680

---------

Co-authored-by: Martin Hořeňovský <martin.horenovsky@gmail.com>

`gmtime*` on Windows fails on dates pre 1970, and because we didn't
check the return code, we would then pass invalid `tm` struct to
`strftime` causing it to assert.

Closes #2944

This was renamed to CATCH_REGISTER_ENUM in 541f1ed1 (Only provide
CATCH_REGISTER_ENUM, 2019-04-21).