Fix unsigned integer known format serialization

[MukundaKatta]

Summary

• serialize unsigned integer known formats as uint8, uint16, uint32, and uint64
• update non-strict integer schema snapshots for u32 and u64
• add regression coverage for unsigned known format serialization

Closes #1527

Verification

• cargo test -p utoipa test_partial_schema_strict_integers
• cargo test -p utoipa test_partial_schema_non_strict_integers --features non_strict_integers
• cargo test -p utoipa serialize_unsigned_integer_known_formats --features non_strict_integers
• cargo fmt --all --check
• git diff --check

[juhaku]

Instead of this, I would rather change the rename_all to lowercase if possible.

[Dzordzu]

It won't be possible, because other types require kebab case. It's either one or another :/

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Snapshot file: utoipa-gen/tests/snapshots/path_derive__derive_path_with_datetime_format_path_parameter.snap
Snapshot: derive_path_with_datetime_format_path_parameter
Source: utoipa-gen/tests/path_derive.rs:447
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Expression: parameters
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
-old snapshot
+new results
────────────┬───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
   14    14 │     "in": "query",
   15    15 │     "name": "start",
   16    16 │     "required": true,
   17    17 │     "schema": {
   18       │-      "format": "date-time",
         18 │+      "format": "datetime",
   19    19 │       "type": "string"
   20    20 │     }
   21    21 │   }
   22    22 │ ]
────────────┴───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
To update snapshots run `cargo insta review`
Stopped on the first failure. Run `cargo insta test` to run all snapshots.

[juhaku]

Oh, you are right. Well this is good to merge. Just needs CHANGELOG.md entry.