feat!: Split TypeArg::Sequence into tuples and lists.

[zrho]

This PR splits up TypeArg::Sequence into TypeArg::List for homogeneous sequences and TypeArg::Tuple for heterogeneous sequences. This is closer to hugr-model and avoids the ambiguous typing of TypeArg::Sequence.

BREAKING CHANGE: TypeArg::Sequence needs to be replaced with TypeArg::List or TypeArg::Tuple in downstream code.

[hugrbot]

This PR contains breaking changes to the public Rust API.

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/v0.41.0/src/lints/enum_no_repr_variant_discriminant_changed.ron

Failed in:
variant TypeArg::Extensions 4 -> 5 in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/types/type_param.rs:200
variant TypeArg::Variable 5 -> 6 in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/types/type_param.rs:208
variant TypeArg::Extensions 4 -> 5 in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/types/type_param.rs:200
variant TypeArg::Variable 5 -> 6 in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/types/type_param.rs:208

--- failure enum_variant_missing: pub enum variant removed or renamed ---

Description:
A publicly-visible enum has at least one variant that 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/v0.41.0/src/lints/enum_variant_missing.ron

Failed in:
variant TypeArg::Sequence, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/types/type_param.rs:183
variant TypeArg::Sequence, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/types/type_param.rs:183

[codecov]

Codecov Report

Attention: Patch coverage is 74.10714% with 29 lines in your changes missing coverage. Please review.

Project coverage is 83.05%. Comparing base (0b091e2) to head (6f7f52d).

Files with missing lines	Patch %	Lines
hugr-core/src/export.rs	0.00%	7 Missing ⚠️
hugr-core/src/import.rs	0.00%	7 Missing ⚠️
hugr-core/src/types/type_param.rs	86.11%	5 Missing ⚠️
hugr-core/src/extension/resolution/types_mut.rs	0.00%	4 Missing ⚠️
hugr-py/src/hugr/tys.py	75.00%	4 Missing ⚠️
hugr-core/src/extension/resolution/types.rs	80.00%	1 Missing ⚠️
hugr-py/src/hugr/_serialization/tys.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2140      +/-   ##
==========================================
- Coverage   83.09%   83.05%   -0.04%     
==========================================
  Files         219      219              
  Lines       41918    41961      +43     
  Branches    37993    38020      +27     
==========================================
+ Hits        34830    34850      +20     
- Misses       5278     5300      +22     
- Partials     1810     1811       +1     

Flag	Coverage Δ
python	85.66% <81.48%> (-0.05%)	⬇️
rust	82.78% <71.76%> (-0.04%)	⬇️

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