chore: add lints to papyrus_common (#1783)

* chore: add free inherit lints in crates

All crates not inheriting from workspace lints fail the workspace lints
and will be handled separately.

Motivation: consistent linting across project and in the CI.

Note: found an unrelated cargo doc bug in starknet_api_test_utils,
not sure why this wasn't triggered thus far, lints are unrelated.

* chore: add lints to papyrus_common

Lior banned `as` repo-wide, unless absolutely necessary.

Nearly all `as` uses can be replaced with `[Try]From` which doesn't have
implicit coercions like `as` (we encountered several bugs due to these
coersions).

Motivation: we are standardizing lints across the repo and CI, instead
of each crate having separate sets of lints.

Co-Authored-By: Gilad Chase <gilad@starkware.com>

crates/papyrus_common/Cargo.toml

@@ -25,3 +25,6 @@ assert_matches.workspace = true
 papyrus_test_utils.workspace = true
 pretty_assertions.workspace = true
 serde_json = { workspace = true, features = ["arbitrary_precision"] }
+
+[lints]
+workspace = true

crates/papyrus_common/src/python_json.rs

@@ -37,7 +37,7 @@ impl Formatter for PythonJsonFormatter {
         let mut buf = [0u16; 2];
         for ch in fragment.chars() {
             if ch.is_ascii() {
-                writer.write_all(&[ch as u8])?;
+                writer.write_all(&[u8::try_from(ch).expect("ASCII fits in u8")])?;
             } else {
                 let slice = ch.encode_utf16(&mut buf);
                 for num in slice {