fix(npmrc): match auth configs by authority and path (#36359)
Auth config lookup treated configured host and path keys as arbitrary
string prefixes. This could select the wrong config for a similarly
named host, a different port, or a sibling path with the same prefix.
Compare scheme-relative keys against the URL's complete authority and
path-segment boundaries while retaining longest-path selection. This
preserves scheme-independent npmrc keys, default-port normalization,
root and nested config behavior, and the existing package-registry
fallback.
Tests:
- `cargo test -p deno_npmrc -- --nocapture`
- `cargo check -p deno_npmrc --all-targets`
- `cargo clippy -p deno_npmrc --all-targets -- -D warnings`
