Change these default values when the jit targets x64 or arm64:

* COMPlus_TC_QuickJitForLoops=1
* COMPlus_TC_OnStackReplacement=1

The upshot is that on x64/arm64 more methods will be jitted at Tier0,
and we will rely on OSR to get out of long-running Tier0 methods.

Other architectures continue to use the old behavior for now, as
OSR is not yet supported for x86 or arm.

…4andArm64