Adjust JIT automated testing for tiered compilation (#18828)

Port of #18828 to 2.2

Make it explicit that most JIT testing does not use tiered compilation regardless of the runtime default
Clone jitstress1/2 and r2r_jitstress1/2 test modes both with and without tiering.
Move the existing tieredcompilation test modes to have the same periodic scheduling as other jit test runs.

Author: noahfalk