Use only UPPERCASE CMake build types and check for it

[davidrohr]

@ktf @pzhristov : @mconcas and me figured out today that compile flags are not set correctly for non-uppercase build types.

Don't know if we want to debug and try to fix it, or just request the build type to be uppercase, which is done in this PR. What do you think?

[github-actions]

REQUEST FOR PRODUCTION RELEASES:
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[ktf]

For the record, in principle whole case sensitivity issue is described here:

https://cmake.org/cmake/help/v3.29/manual/cmake-buildsystem.7.html#case-sensitivity

and the "strong" convention is described a few lines below:

https://cmake.org/cmake/help/v3.29/manual/cmake-buildsystem.7.html#id38

I would personally prefer we stick to the convention and fix the cases where the wrong casing is used.

[ktf]

Or if you prefer, if I understand correctly, the "safe" pattern is what is done in #12886

[ktf]

As discussed, let's use #12886