Add an option for using clang format and set it to off by default

[jmcarcell]

BEGINRELEASENOTES

• Add an option for using clang format and set it to off by default. It is significantly slower to run cmake with this option on.

ENDRELEASENOTES

I don't think most users care and we could run clang-format for the builds in the stacks, but if you are building I think you would rather get to whatever you want to do sooner. We could turn on the option for the stack builds but for developer builds the OFF option makes more sense in my opinion.

I have some times for configure without downloading the test files. Rebuild means when for example you make a change in a CMakeLists.txt file so that configure has to run again when you try to build:

On my machine (all local):

	From scratch	Rebuild
With clang-format	16 s	14 s
Without clang-format	6 s	4 s

On a build node (Alma 9):

	From scratch	Rebuild
With clang-format	27 s	20 s
Without clang-format	20 s	13 s

[tmadlener]

I think cmake -DPODIO_USE_CLANG_FORMAT=OFF should already work right now without these changes, since we set this here:

podio/cmake/podioMacros.cmake

Lines 108 to 109 in e44af47

	set(PODIO_USE_CLANG_FORMAT AUTO CACHE STRING "Try to use clang-format to format the code generated by podio")
	set_property(CACHE PODIO_USE_CLANG_FORMAT PROPERTY STRINGS AUTO ON OFF)

[jmcarcell]

Yes, the change here would be to have it OFF by default and for stacks and whoever wants it to have it ON since it doesn't have any impact unless you look at the files (and how often does this happen anyway?)

[tmadlener]

If we set this to OFF by default, can we at least have one CI workflow where we have it AUTO / ON with a suitable clang-format available? Just to avoid inadvertently breaking anything in the future.