[Static Runtime] Make canEnableStaticRuntime examine sub-blocks (#87396)
Summary:
Someone was running into problems where
1) Static Runtime enablement would fail
2) We would try to fall back to the JIT interpreter *after trying to create `StaticModule`*
3) The fallback fails because Static Runtime mangled the graph.
We don't want to prevent Static Runtime from mutating its input due to memory concerns. The intent of `canEnableStaticRuntime` is to catch issues in the module before Static Runtime messes with it.
With this diff, `StaticModule` instantiation can be avoided by querying `canEnableStaticRuntime` and the issue is fixed.
Test Plan: New unit test
Differential Revision: D40564452
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87396
Approved by: https://github.com/tenpercent
