CMakeDeps: remove warning about existing alias

[BobIsOnFire]

Changelog: Fix: CMakeDeps: Remove "Target name ... already exists" warning about duplicating aliases.
Docs: omit

This PR benefits #14560 (and #12958)

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[memsharded]

Thanks for your contribution @BobIsOnFire

I think I'd advocate for removing the warning completely, I think it is there to protect against colliding aliases from different packages, but that check should better be done globally, I'll check with the team.

[memsharded]

It seems this warning is more problematic than helpful for most users. Lets do the following:

• Please remove the warnings completely from CMake code (do you want to do it in this same PR @BobIsOnFire ?). Note: there is a test test_collide_component_alias that explicitly checks for this warning, this test can remove the check, and add a comment that this is possible (alias collision), and it will not warn at this moment.
• As a future thing, we could consider checking in the CMakeDeps python code possible aliases colisions and warn, or even error from there.

[BobIsOnFire]

Hi @memsharded

Thanks! I have updated branch to remove warning / adjust tests.