[PERF] Backoff Supervisor uses Expression based Props

[to11mtm]

Related to #4698

Version Information
1.4.x

Describe the performance issue
Backoff Supervisor Props use Expressions, which has a large perf impact for cases where an actor is created semi-transiently but still needs backoff.

Data and Specs
See #4698 for details. The benchmarks there illustrate the overall concern well enough.

Expected behavior
Don't use Expression based props where it's possible transient actors are being created.

Actual behavior
We use expression based props and it hurts perf by a significant margian

Environment
N/A

Additional context
This is not as big a problem for long lived actors.

We should still consider having an issue for other internals of akka where this may come up, even if it means more diligence from maintainers (although, FWIW, unit tests should cover when someone gets it wrong).