Set compiler.cstd in host profile

[jhol]

The cstd setting was added to Conan in v2.4.0. Similar to cppstd, it is used to indicate the selected C language standard.

The branch of this PR is based upon the tidy-ups branch from #656, which has not yet been merged to develop2, hence why the additional patches are also visible.

[jhol]

@valgur @memsharded would it be possible to get this merged?

[memsharded]

Hi @jhol

Thanks for your PR and sorry it was not reviewed back then.

The problem with this PR is that it creates a profile that is not aligned with the default Conan profiles.
conan profile detect will not define the cstd yet, at the moment it is considered an opt-in as it can change some things, effect the package_id, etc, so it is a bit risky to be defined by default.

I am not fully opposed to it, but we need to carefully consider this, I'll try to review it with @jcar87 when possible, thanks for the ping!

[jhol]

The problem with this PR is that it creates a profile that is not aligned with the default Conan profiles.
conan profile detect will not define the cstd yet, at the moment it is considered an opt-in as it can change some things, effect the package_id, etc, so it is a bit risky to be defined by default.

Is there a way we can make this opt-in or opt-out in conan_provider.cmake? This is necessary in my project so that the correct cstd can be passed through to conan recipes for cmake-powered projects.