breaking: remove base, asset, and resolveRoute

[teemingc]

This PR removes the deprecated base, asset and resolveRoute APIs from $app/paths.

It also removes/refactors some tests related to those APIs. For the removed tests, I wasn't sure if they were superseded by some resolve and assets tests or if we still needed them.

Requires sveltejs/svelte.dev#1848 to get the site building

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🦋 Changeset detected

Latest commit: 5cd1ccd

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Major

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-15507-svelte.vercel.app/