fix(dev): improve server build asset handling

[markdalgleish]

We currently log a message during the build when moving assets from the server build to the client, but we weren't logging anything when cleaning server assets that already exist in the client build. This led to some confusion because Vite logs that these files were generated, but after the build has finished the assets are no longer there.

To avoid this confusion, we now log whenever assets are handled in any way, not just when they're moved.

While working on this, I also realised that we don't honour the consumer's build.ssrEmitAssets option if they explicitly want to keep these assets, so the logic and logging has also been updated to account for this.

Before:

After:

[changeset-bot]

🦋 Changeset detected

Latest commit: e35e15f

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

This PR includes changesets to release 11 packages

Name	Type
@react-router/dev	Patch
@react-router/fs-routes	Patch
@react-router/remix-routes-option-adapter	Patch
create-react-router	Patch
react-router	Patch
react-router-dom	Patch
@react-router/architect	Patch
@react-router/cloudflare	Patch
@react-router/express	Patch
@react-router/node	Patch
@react-router/serve	Patch

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