This fixes the cases where
```js
import 'imp2/index.js';
import 'imp3/foo.js';
```
And these files lives in `assets` as:
```
imp2/index.ts
imp3/foo.ts
```
Fixes#10527
* Redo the server error template
* Always add the content file context if relevant
* Remove some now superflous error string matching
* Move the server error template to _server/error.html
* Add file context (with position) to codeblock render blocks
* Improve JS build errors
Fixes#9892Fixes#9891Fixes#9893
