Building on #58293, this expands escaping of url-unsafe characters in
paths to “required” scripts and styles in the app renderer.
This also refactors the test introduced in #58293 and expands it to
include stylesheet references as well as checking resources in the head,
which include special characters like turbopack references like
`[turbopack]`.
Test Plan: `TURBOPACK=1 pnpm test-dev
test/e2e/app-dir/resource-url-encoding`
Closes PACK-2911
