Move trace calculation; refactor from method to function

[FabijanC]

Usage related changes

None

Development related changes

• Move trace calculation to a separate module
• Replace Starknet self param with CachedState param in trace creation
• Body of create_trace is basically unmodified, just moved

Checklist:

• Applied formatting - ./scripts/format.sh
• No linter errors - ./scripts/clippy_check.sh
• No unused dependencies - ./scripts/check_unused_deps.sh
• Performed code self-review
• Rebased to the last commit of the target branch (or merged it into my branch)
• Documented the changes
• Linked the issues which this PR resolves
• Checked the TODO section in README.md if this PR resolves it
• Updated the tests
• All tests are passing - cargo test

[marioiordanov]

Isn't it possible to pass an immutable state to create_trace, rather than mutable

[FabijanC]

Isn't it possible to pass an immutable state to create_trace, rather than mutable

I re-checked. I tried changing &mut to &, but eventually got to FunctionInvocation::try_from_call_info, which operates on state_reader::get_class_hash_at, which requires mutability.