JIT: update jit config defaults for PGO (#49267)

JIT: update jit config defaults for PGO (#49267)

Enable edge profiling by default, when jitting, or when prejitting for R2R.
Keep block profiling there for classic ngen (so there is an entry probe).

Enable minimal probing by default, when jitting. Keep full probing there for
prejitting so presence of counts in a method implies method was executed.

Enable class profiling by default when jitting. Still TBD if we will also
do this when prejitting.

Enable guarded devirtualization by default (will only kick in for PGO).

Adjust experimental CI legs to reflect the above.

Net effect is that when jitting, COMPlus_TieredPGO=1 turns on dynamic PGO
with the expected set of behaviors, without any other options.

We'll still need to set COMPlus_TC_QuickJitForLoops=1 to have methods with
loops pass through Tier0.