Replace assert_module_ok! with trycmd tests 🧑‍💻

[jmackie]

Added assert-rs/trycmd in #87 and I'm a fan. Seems like a nice way of handling acceptance tests, particularly for a compiler project like this.

I don't really like the assert_module_ok! and assert_module_err! testing macros, and I think https://github.com/assert-rs/trycmd could do better. Hence this PR replaces the former with the latter 👌.

[codecov]

Codecov Report

Merging #91 (0fcf40b) into main (ee223c0) will decrease coverage by 2.76%.
The diff coverage is 4.76%.

@@            Coverage Diff             @@
##             main      #91      +/-   ##
==========================================
- Coverage   78.48%   75.71%   -2.77%     
==========================================
  Files         118      111       -7     
  Lines        8132     7998     -134     
==========================================
- Hits         6382     6056     -326     
- Misses       1750     1942     +192     

Impacted Files	Coverage Δ
crates/ditto-ast/src/module.rs	100.00% <ø> (ø)
crates/ditto-checker/src/module/exports/mod.rs	100.00% <ø> (ø)
...ecker/src/module/foreign_value_declarations/mod.rs	100.00% <ø> (ø)
crates/ditto-checker/src/module/imports/mod.rs	90.51% <ø> (ø)
crates/ditto-checker/src/module/mod.rs	100.00% <ø> (ø)
...cker/src/module/type_declarations/tests/acyclic.rs	100.00% <ø> (ø)
...ker/src/module/type_declarations/tests/toposort.rs	100.00% <ø> (ø)
...ker/src/module/value_declarations/tests/acyclic.rs	100.00% <ø> (ø)
...er/src/module/value_declarations/tests/toposort.rs	100.00% <ø> (ø)
...es/ditto-checker/src/typechecker/coverage/tests.rs	100.00% <ø> (ø)
... and 11 more

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