refactor(language-service): Cleanup TypescriptHost (#32017)

Cleanup the logic in TypeScriptHost as to when langauge service state
should be synchronized with the editor state.

The model employed follows that of tsserver, in which case it is the
caller's responsiblity to synchronize host data before any LS methods
are called.

PR Close #32017

packages/language-service/src/ts_plugin.ts

@@ -18,6 +18,7 @@ const projectHostMap = new WeakMap<tss.server.Project, TypeScriptServiceHost>();
 export function getExternalFiles(project: tss.server.Project): string[]|undefined {
   const host = projectHostMap.get(project);
   if (host) {
+    host.getAnalyzedModules();
     const externalFiles = host.getTemplateReferences();
     return externalFiles;
   }