lints: Distingiush between "runtime error" vs "lint check"

Add an internal error type, and switch to using a nested
`Result<Result<>>` approach for lints. This allows
cleanly distinguishing between e.g. "we failed to open
a file" from "the lint correctly/successfully found something wrong".

This is also helpful for being able to skip lint failures - we
wouldn't want to silently skip runtime failures.

Signed-off-by: Colin Walters <[email protected]>

Author: cgwalters

Cargo.lock

@@ -46,6 +46,7 @@ xshell = { version = "0.2.6", optional = true }
 uuid = { version = "1.8.0", features = ["v4"] }
 tini = "1.3.0"
 comfy-table = "7.1.1"
+thiserror = "2.0.11"
 
 [dev-dependencies]
 indoc = { workspace = true }