Fix a number of typescript issues (#32308)

- Prefer
[window.location.assign](https://developer.mozilla.org/en-US/docs/Web/API/Location/assign)
over assigning to
[window.location](https://developer.mozilla.org/en-US/docs/Web/API/Window/location)
which typescript does not like. This works in all browsers including
PaleMoon.
- Fix all typescript issues in `web_src/js/webcomponents`, no behaviour
changes.
- ~~Workaround bug in `@typescript-eslint/no-unnecessary-type-assertion`
rule.~~
- Omit vendored file from type checks.
- `tsc` error count is reduce by 53 with these changes.

web_src/js/webcomponents/origin-url.ts

@@ -1,7 +1,7 @@
 // Convert an absolute or relative URL to an absolute URL with the current origin. It only
 // processes absolute HTTP/HTTPS URLs or relative URLs like '/xxx' or '//host/xxx'.
 // NOTE: Keep this function in sync with clone_script.tmpl
-export function toOriginUrl(urlStr) {
+export function toOriginUrl(urlStr: string) {
   try {
     if (urlStr.startsWith('http://') || urlStr.startsWith('https://') || urlStr.startsWith('/')) {
       const {origin, protocol, hostname, port} = window.location;