chore: remove starknet-contract-class

[MegaRedHand]

Description

This PR removes the starknet-contract-class crate that is no longer used. The functionality was moved again into starknet_in_rust.

Along with that, removes the invalid override options from dtolnay/rust-toolchain actions in the CI.

Checklist

• Linked to Github Issue
• Unit tests added
• Integration tests added.
• This change requires new documentation.
  • Documentation has been added/updated.

[codecov-commenter]

Codecov Report

Merging #766 (794ac25) into main (d3f4f03) will increase coverage by 0.04%.
The diff coverage is 93.75%.

@@            Coverage Diff             @@
##             main     #766      +/-   ##
==========================================
+ Coverage   92.45%   92.49%   +0.04%     
==========================================
  Files          51       50       -1     
  Lines       11945    11893      -52     
==========================================
- Hits        11044    11001      -43     
+ Misses        901      892       -9     

Impacted Files	Coverage Δ
...re/contract_address/deprecated_contract_address.rs	93.71% <ø> (ø)
...c/core/contract_address/sierra_contract_address.rs	0.00% <ø> (ø)
src/execution/execution_entry_point.rs	97.35% <ø> (ø)
src/execution/mod.rs	97.55% <ø> (ø)
src/parser_errors.rs	0.00% <ø> (ø)
src/serde_structs/mod.rs	100.00% <ø> (ø)
src/services/api/contract_class_errors.rs	0.00% <ø> (ø)
src/state/cached_state.rs	93.45% <ø> (ø)
src/state/in_memory_state_reader.rs	91.24% <ø> (ø)
src/syscalls/business_logic_syscall_handler.rs	77.56% <ø> (ø)
... and 13 more