[FIRRTL] IMConstProp (and others) should preserve InstanceGraph

Nobody has claimed this yet.

Seems like we are not preserving the `InstanceGraph` analysis in `IMConstProp`.
We have to look at all the passes that are using the `InstanceGraph` analysis, and if it can be preserved.
In the following runtime output, any pass with `(A) circt::firrtl::InstanceGraph` is redoing the analysis.
```
----User Time---- ----Wall Time---- ----Name----
35.7049 ( 6.6%) 35.7049 ( 13.3%) FIR Parser
466.8056 ( 86.6%) 195.7462 ( 73.1%) 'firrtl.circuit' Pipeline
60.0645 ( 11.1%) 3.6523 ( 1.4%) 'firrtl.module' Pipeline
55.9135 ( 10.4%) 3.4582 ( 1.3%) CSE
0.1137 ( 0.0%) 0.0164 ( 0.0%) (A) DominanceInfo
4.0435 ( 0.8%) 0.3411 ( 0.1%) LowerCHIRRTLPass
13.9256 ( 2.6%) 13.9256 ( 5.2%) InferWidths
15.9592 ( 3.0%) 15.9592 ( 6.0%) InferResets
0.7073 ( 0.1%) 0.7073 ( 0.3%) (A) circt::firrtl::InstanceGraph
4.8849 ( 0.9%) 4.8849 ( 1.8%) WireDFT
10.3873 ( 1.9%) 10.3873 ( 3.9%) PrefixModules
18.9497 ( 3.5%) 18.9497 ( 7.1%) LowerFIRRTLTypes
172.5599 ( 32.0%) 15.7106 ( 5.9%) 'firrtl.module' Pipeline
28.5536 ( 5.3%) 1.9058 ( 0.7%) ExpandWhens
0.3131 ( 0.1%) 0.1318 ( 0.0%) RemoveResets
132.6794 ( 24.6%) 12.9047 ( 4.8%) Canonicalizer
10.9484 ( 2.0%) 0.8854 ( 0.3%) InferReadWrite
13.3058 ( 2.5%) 13.3058 ( 5.0%) Inliner
14.8439 ( 2.8%) 14.8439 ( 5.5%) IMConstProp
0.5209 ( 0.1%) 0.5209 ( 0.2%) (A) circt::firrtl::InstanceGraph
7.0860 ( 1.3%) 7.0860 ( 2.6%) BlackBoxReader
0.5011 ( 0.1%) 0.5011 ( 0.2%) (A) circt::firrtl::InstanceGraph
47.1971 ( 8.8%) 47.1971 ( 17.6%) GrandCentral
6.7771 ( 1.3%) 6.7771 ( 2.5%) GrandCentralTaps
0.5238 ( 0.1%) 0.5238 ( 0.2%) (A) circt::firrtl::InstanceGraph
43.7669 ( 8.1%) 7.1336 ( 2.7%) 'firrtl.module' Pipeline
0.1425 ( 0.0%) 0.0246 ( 0.0%) GrandCentralSignalMappings
43.3741 ( 8.0%) 7.1308 ( 2.7%) Canonicalizer
6.0484 ( 1.1%) 6.0484 ( 2.3%) RemoveUnusedPorts
0.4631 ( 0.1%) 0.4631 ( 0.2%) (A) circt::firrtl::InstanceGraph
3.6972 ( 0.7%) 3.6972 ( 1.4%) CreateSiFiveMetadata
0.4078 ( 0.1%) 0.4078 ( 0.2%) (A) circt::firrtl::InstanceGraph
6.1606 ( 1.1%) 6.1606 ( 2.3%) EmitOMIR
```

Start by tracing the FIRRTL passes named in the runtime output, especially IMConstProp, BlackBoxReader, GrandCentral, RemoveUnusedPorts, and CreateSiFiveMetadata, and inspect their use of the InstanceGraph analysis. Compare which passes can preserve that analysis after running. Done means the applicable passes preserve InstanceGraph and the runtime output no longer shows avoidable recomputation.

Written by the indexing model from the issue text.