Improve prefetch behaviour for browsers

[bluwy]

Changes

Closes #10464

• This PR makes all prefetch strategies to use <link rel="prefetch"> if supported, or else fall back to fetch().
• It also applies the same for the programmatic prefetch() API, unless the with: 'link' | 'fetch' option is passed. The with option is deprecated as it's better to use link whenever possible.

More explanation for why this change is made at #10464 (comment)

Testing

The existing tests should pass. Testing is a bit tricky because this mainly matters for Firefox and Safari but we don't have those setup. I think manual testing should be enough for now as the prefetch code is isolated and doesn't changed often.

Docs

withastro/docs#8246

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[ematipico]

@bluwy what should we do to test it on Firefox? I can help

[bluwy]

We probably need to update playwright.config.js projects to also test on Firefox etc. But we don't want to run all tests on Firefox, so we may need a second playwright config that only runs specific tests? And I think that should be enough, we can also run it for the view transitions tests.

We also need to update this to install the firefox etc binaries:

astro/package.json

Lines 33 to 34 in 1c59059

	"test:e2e": "cd packages/astro && pnpm playwright install chromium && pnpm run test:e2e",
	"test:e2e:match": "cd packages/astro && pnpm playwright install chromium && pnpm run test:e2e:match",

[ematipico]

Awesome, I can make a PR for that if you're happy

[Princesseuh]

Isn't it somewhat expensive to do this on every link? Could it be done once?

[bluwy]

I benchmarked this locally and there isn't a big difference in perf from what I can tell compared to caching, so I kept this direct approach, and to save some bytes.

[bholmesdev]

The conditional checks look right to me. Glad we're getting with the times!

[ematipico]

I added Firefox to the e2e tests, however some of the tests fail e.g. view transitions