This simplified variant supports only a subset of the functionality
in `std::unique_ptr<T>`. `Catch::Detail::unique_ptr<T>` only supports
single element pointer (no array support) with default deleter.
By removing the support for custom deleters, we also avoid requiring
significant machinery to support EBO, speeding up instantiations of
`unique_ptr<T>` significantly. Catch2 also currently does not need
to support `unique_ptr<T[]>`, so that is not supported either.
As far as I know, only a few users actually use it, but these changes
allow us to avoid including a surprising amount of code in the main
compilation path.
As Clara is no longer maintained as a separate project, the
implementation was moved to the internal subfolder of top-level
folder. This removes one folder and avoids potential user confusion.
Also simplified the convenience header checking script accordingly.
There are two reasons for this:
1) It is highly unlikely that someone has use for this header,
which has no customization points and only provides simplest
possible main, and cannot link the static library which also
provides a default main implementation.
2) It being a header was causing extra complications with
the convenience headers, and our checking script. This would either
require special handling in the checking script, or would break user's
of the main convenience header.
All in all, it is simpler and better in the long term to remove it,
than to fix its problems.
The naming scheme is simple, to include all matchers, include header
`catch2/matchers/catch_matchers_all.hpp`. To include **everything**,
include `catch2/catch_all.hpp`.
