Bug 1809683 [wpt PR 37881] - Remove `prefetch-src` and use least-restrictive directiv...

Bug 1809683 [wpt PR 37881] - Remove `prefetch-src` and use least-restrictive directive instead, a=testonly

Automatic update from web-platform-tests
Remove `prefetch-src` and use least-restrictive directive instead

This implements the spec:
https://w3c.github.io/webappsec-csp/#does-resource-hint-violate-policy

- Remove prefetch-src and anything related
- When CSP-testing a prefetch request, test if default-src or any
  other directive allows for that source
- Remove use of 'prefetch-src' from nav-speculation
  (spec issue: https://github.com/WICG/nav-speculation/issues/235)
- Add multiple WPTs to cover this.

Note that prefetch-src was erroneously enabled by default in 2021.

Bug: 1406444
Change-Id: I46bb76edaf7b280443ab4c3d4f6470bc30509d51
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4154428
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Noam Rosenthal <nrosenthal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1104223}

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wpt-commits: 021d1b5eb068f8f9a0791f70660a314508160b02
wpt-pr: 37881