Fix a number of Typescript issues (#31877)

Typescript error count is reduced from 633 to 540 with this. No runtime
changes except in test code.

web_src/js/utils/url.ts

@@ -1,12 +1,12 @@
-export function pathEscapeSegments(s) {
+export function pathEscapeSegments(s: string): string {
   return s.split('/').map(encodeURIComponent).join('/');
 }
 
-function stripSlash(url) {
+function stripSlash(url: string): string {
   return url.endsWith('/') ? url.slice(0, -1) : url;
 }
 
-export function isUrl(url) {
+export function isUrl(url: string): boolean {
   try {
     return stripSlash((new URL(url).href)).trim() === stripSlash(url).trim();
   } catch {