Add tool configuration to specify CMake executable path (#12701)

[iskunk]

Changelog: Feature: Add a tools.cmake:cmake_program configuration item to allow specifying the location of the desired CMake executable.
Docs: conan-io/docs#3232

Fixes: #12701

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[CLAassistant]

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[memsharded]

Thanks for your contribution.

Could you please add some unit test that will cover this new conf functionality? One in the unittest folder could be enough

If you want this functionality to be included in next 2.0.X releases, please target the PR to the release/2.0 branch, it can be added there, no risk.

[iskunk]

All right, I've re-targeted the PR to release/2.0, and added my best guess at a unit test for the new configuration item. Please double-check it.

[memsharded]

Looks good.
The only remaining issue is that moving the branches targets for the PR created some confussion for the CLA-assistant. If it doesn't automatically resolve (sometimes after some time CLA-assistant is able to figure out the contributors correctly), it might need to close it and open a new PR, lets see how it goes.
Thanks again for your contribution.