[v7] Validate client-side navigation targets

[brophdawg11]

Backport of #15445 to v7.

This improves consistency when handling client-side navigation targets by validating both the supplied destination and its resolved URL.

• Programmatic navigations reject unsupported external destinations.
• Client-side redirects continue to support explicit external destinations.
• External links and server-side redirects remain supported.

[github-actions]

Preview Build Available

Preview builds have been created for this PR. You can install react-router using:

pnpm install "remix-run/react-router#preview/pr-15446&path:packages/react-router"

And/or install other packages via:

pnpm install "remix-run/react-router#preview/pr-15446&path:packages/react-router-dev"
pnpm install "remix-run/react-router#preview/pr-15446&path:packages/react-router-express"
pnpm install "remix-run/react-router#preview/pr-15446&path:packages/react-router-node"
pnpm install "remix-run/react-router#preview/pr-15446&path:packages/react-router-serve"

These preview builds will be updated automatically as you push new commits.