[firrtl] Passes don't indicate they "preserve all" analyses when they don't do anything

The BlackBoxReader pass often doesn't do anything, and ExpandWhens doesn't when run on low firrtl. They should indicate that they preserves all, which prevents it from invalidating analyses and will provide a speedup when/if this gets resolved: https://bugs.llvm.org/show_bug.cgi?id=50701

The pass just needs to call `markAllAnalysesPreserved();`

### Todo

- [x] BlackBoxMemory (#1274)
- [x] BlackBoxReader (#1274)
- [x] InferWidths (#1274)
- [x] ExpandWhens (#1272)
- [ ] IMConstPop
- [ ] LowerTypes
- [ ] ModuleInliner
- [ ] GeneratorCallout
- [ ] HWStubExternalModulesPass
- [ ] SVExtractTestCode

Start by locating the implementations of the remaining passes listed in the Todo section: IMConstPop, LowerTypes, ModuleInliner, GeneratorCallout, HWStubExternalModulesPass, and SVExtractTestCode. Check how each pass handles the no-op case and use the existing markAllAnalysesPreserved() call pattern; done means the remaining unchecked passes indicate that all analyses are preserved when appropriate.

Written by the indexing model from the issue text.