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::Variable 4 -> 5 in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/types/type_param.rs:196
variant TypeArg::Variable 4 -> 5 in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-core/src/types/type_param.rs:196

--- 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:180
variant TypeArg::Sequence, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-core/src/types/type_param.rs:180

[codecov]

Codecov Report

Attention: Patch coverage is 74.56140% with 29 lines in your changes missing coverage. Please review.

Project coverage is 82.00%. Comparing base (9b3fbb4) to head (6dabb3c).

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	84.21%	6 Missing ⚠️
hugr-py/src/hugr/tys.py	75.00%	4 Missing ⚠️
hugr-core/src/extension/resolution/types.rs	66.66%	2 Missing ⚠️
hugr-core/src/extension/resolution/types_mut.rs	50.00%	1 Missing and 1 partial ⚠️
hugr-py/src/hugr/_serialization/tys.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2140      +/-   ##
==========================================
- Coverage   82.04%   82.00%   -0.05%     
==========================================
  Files         234      234              
  Lines       41704    41754      +50     
  Branches    37616    37650      +34     
==========================================
+ Hits        34216    34239      +23     
- Misses       5513     5540      +27     
  Partials     1975     1975              

Flag	Coverage Δ
python	85.30% <81.48%> (-0.05%)	⬇️
rust	81.64% <72.41%> (-0.05%)	⬇️

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