feat: (WIP) Add insert_link_hugr to add entrypoint subtree AND link

[acl-cqc]

Follows #2529

• Add insert_link_hugr and insert_link_view taking a node under which to add the entrypoint
• Add reachability analysis and NewFuncHandling::AddIfReached,ErrorIfReached
• Extend NameLinkingPolicy to allow setting how to handle to new names in the source Hugr, and a switch to filter out unreachable private funcs

TODO

• Tests!!
• What about when the entrypoint is one of the functions of the source Hugr? Probably this should work OK (assuming the parent is the target's module_root, then basically just forces that function to be a reachable one? Or should we e.g. force adding it even contrary to the signature-conflict/multiple-impl handling used for other functions?)

closes #2517

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 65 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.91%. Comparing base (5ca0e5f) to head (e5e1ad2).

Files with missing lines	Patch %	Lines
hugr-core/src/hugr/linking.rs	57.25%	55 Missing and 1 partial ⚠️
hugr-core/src/call_graph.rs	85.93%	7 Missing and 2 partials ⚠️

Additional details and impacted files

@@                Coverage Diff                @@
##           acl/link_hugr    #2555      +/-   ##
=================================================
- Coverage          83.00%   82.91%   -0.10%     
=================================================
  Files                254      255       +1     
  Lines              47781    47933     +152     
  Branches           43292    43444     +152     
=================================================
+ Hits               39663    39743      +80     
- Misses              6055     6124      +69     
- Partials            2063     2066       +3     

Flag	Coverage Δ
python	91.42% <ø> (ø)
rust	82.03% <66.66%> (-0.11%)	⬇️

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[hugrbot]

This PR contains breaking changes to the public Rust API.
Please deprecate the old API instead (if possible), or mark the PR with a ! to indicate a breaking change.

cargo-semver-checks summary

--- failure enum_no_repr_variant_discriminant_changed: enum variant had its discriminant change value ---

Description:
The enum's variant had its discriminant value change. This breaks downstream code that used its value via a numeric cast like `as isize`.
      ref: https://doc.rust-lang.org/reference/items/enumerations.html#assigning-discriminant-values
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.43.0/src/lints/enum_no_repr_variant_discriminant_changed.ron

Failed in:
variant NewFuncHandling::Add 1 -> 2 in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/hugr/linking.rs:351

--- failure enum_variant_added: enum variant added on exhaustive enum ---

Description:
A publicly-visible enum without #[non_exhaustive] has a new variant.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#enum-variant-new
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.43.0/src/lints/enum_variant_added.ron

Failed in:
variant NameLinkingError:NoNewNames in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/hugr/linking.rs:408

[acl-cqc]

I'll remove this, it can follow in another PR