feat: Detect subgraphs that are completely independent from inputs or outputs

[Rumata888]

Description

Problem*

Currently a developer can create a circuit that would use unconstrained values in such a way, that a part of the circuit becomes completely disconnected from the circuit inputs or outputs, making this part completely useless as it can be taken out of any proof. This PR introduces an Ssa pass that informs the user of this issue.

Summary*

An Ssa pass that detects some underconstraining issues

Additional Context

Documentation*

Check one:

• [x] No documentation needed.
• [ ] Documentation included in this PR.
• [ ] [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• [x] I have tested the changes locally.
• [x] I have formatted the changes with Prettier and/or cargo fmt on default settings.