[MASTER] Add x86 and x64 builders/testers for -DSAFE_TESTS_ONLY=1

[ColinFinck]

As requested by @tkreuzer, here comes an extra tester for a rostests build with -DSAFE_TESTS_ONLY=1.
This allows @tkreuzer to implement a list of safe tests in the main repo and only run these (without crash recovery).

Next to the testers, I needed to add an extra builder for x86 and x64.
This is necessary, because:

• The x64 builder is a Windows MSVC builder, but the x64 tester is a Linux server with KVM. This is why we can't have a combined builder/tester for x64 (and I did it the same for x86 for consistency).
• We can't just add another step to the existing x86/x64 builders, because we need to transfer the bootcdregtest to the tester after build. They are distinguished via their suffix, and there can only be one suffix per builder.

I took the opportunity to clean up our BuildBot master.cfg, deduplicate lots of copy-pastes, and remove commented out and long obsoleted configs.
Therefore, this PR is best to be reviewed commit by commit.

[ColinFinck]

New idea: https://chat.reactos.org/reactos/pl/3e58d885c7gody6osqpkeq4cph

[tkreuzer]

I cannot really judge the code, but I like to have this thing. So approved.