feat: Debug::fmt for signed integers

[milancermak]

Feature Request

Describe the Feature Request

It should be possible to print signed integers (i8...i128). Currently, trying to println!("{}", an_i128); results in an error similar to this

error: Trait has no implementation in context: core::fmt::Display::<core::integer::i128>
 --> /Users/m/projects/bibliodao/lordship/src/tests/test_velords.cairo[println_macro][writeln_macro]:3:31
    match core::fmt::Display::fmt(__write_macro_arg0__, ref __formatter_for_print_macros__) {
                              ^*^

Error: Failed to compile test artifact, for detailed information go through the logs above

Describe Preferred Solution

Both Debug and Display should be implemented. A sign should be prepended to the value in case it's negative.

Additional Context

scarb --version
scarb 2.6.3 (e6f921dfd 2024-03-13)
cairo: 2.6.3 (https://crates.io/crates/cairo-lang-compiler/2.6.3)
sierra: 1.5.0

Missing this feature also means it's currently not possible to use assert_eq! on signed integers.

If the feature request is approved, would you be willing to submit a PR?
(Help can be provided if you need assistance submitting a PR)

• Yes
• No