refactor!: Replace Subcircuit with SiblingSubgraph

[acl-cqc]

This is the first step towards a new (more efficient) Subcircuit; the current offers no real advantage over SiblingSubgraph, so use that instead.

BREAKING CHANGE: Subcircuit is gone, use SiblingSubgraph instead; .subcircuit() -> .subgraph()

This is not a breaking change for python,

BEGIN_COMMIT_OVERRIDE
refactor: Replace Subcircuit with SiblingSubgraph (#1288)
END_COMMIT_OVERRIDE

[codecov]

Codecov Report

❌ Patch coverage is 85.29412% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.56%. Comparing base (0f1d700) to head (f888d39).
⚠️ Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
tket/src/portmatching/matcher.rs	33.33%	4 Missing ⚠️
tket/src/rewrite.rs	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1288      +/-   ##
==========================================
+ Coverage   79.46%   79.56%   +0.10%     
==========================================
  Files         160      160              
  Lines       20378    20571     +193     
  Branches    19446    19605     +159     
==========================================
+ Hits        16194    16368     +174     
- Misses       3201     3222      +21     
+ Partials      983      981       -2     

Flag	Coverage Δ
python	92.92% <ø> (+0.27%)	⬆️
qis-compiler	100.00% <ø> (ø)
rust	78.89% <85.29%> (+0.07%)	⬆️

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[hugrbot]

This PR contains breaking changes to the public Rust API.

cargo-semver-checks summary

    Building tket v0.16.0 (current)
     Built [  41.694s] (current)
   Parsing tket v0.16.0 (current)
    Parsed [   0.095s] (current)
  Building tket v0.16.0 (baseline)
     Built [  40.452s] (baseline)
   Parsing tket v0.16.0 (baseline)
    Parsed [   0.091s] (baseline)
  Checking tket v0.16.0 -> v0.16.0 (assume minor change)
   Checked [   0.097s] 159 checks: 157 pass, 2 fail, 0 warn, 41 skip

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.45.0/src/lints/inherent_method_missing.ron

Failed in:
PatternMatch::subcircuit, previously in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/portmatching/matcher.rs:99
PatternMatch::subcircuit, previously in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/portmatching/matcher.rs:99
CircuitRewrite::subcircuit, previously in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/rewrite.rs:117

--- failure struct_missing: pub struct removed or renamed ---

Description:
A publicly-visible struct cannot be imported by its prior path. A `pub use` may have been removed, or the struct itself may have been renamed or removed entirely.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.45.0/src/lints/struct_missing.ron

Failed in:
struct tket::rewrite::Subcircuit, previously in file /home/runner/work/tket2/tket2/BASELINE_BRANCH/tket/src/rewrite.rs:30

   Summary semver requires new major version: 2 major and 0 minor checks failed
  Finished [  84.105s] tket
  Building tket-qsystem v0.22.0 (current)
     Built [  42.305s] (current)
   Parsing tket-qsystem v0.22.0 (current)
    Parsed [   0.028s] (current)
  Building tket-qsystem v0.22.0 (baseline)
     Built [  42.475s] (baseline)
   Parsing tket-qsystem v0.22.0 (baseline)
    Parsed [   0.028s] (baseline)
  Checking tket-qsystem v0.22.0 -> v0.22.0 (assume minor change)
   Checked [   0.046s] 159 checks: 159 pass, 41 skip
   Summary no semver update required
  Finished [  87.010s] tket-qsystem

[doug-q]

Thanks