Remove web worker support from microsoft-authentication extension (#276762)

* Initial plan

* Remove web worker support from microsoft-authentication extension

- Remove browser entry point from package.json
- Remove browser webpack configuration
- Remove browser-specific scripts (compile-web, watch-web)
- Remove src/browser/ directory with browser-specific implementations
- Remove ExtensionHost.WebWorker enum value
- Remove supportsWebWorkerExtensionHost flags from all flows
- Simplify authProvider.ts by removing web worker detection logic
- Remove web worker test case from flows.test.ts
- Successfully compiled with 0 errors

Co-authored-by: TylerLeonhardt <2644648+TylerLeonhardt@users.noreply.github.com>

* couple references

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

extensions/microsoft-authentication/tsconfig.json

@@ -4,10 +4,7 @@
 		"outDir": "./out",
 		"noFallthroughCasesInSwitch": true,
 		"noUnusedLocals": false,
-		"skipLibCheck": true,
-		"lib": [
-			"WebWorker"
-		]
+		"skipLibCheck": true
 	},
 	"include": [
 		"src/**/*",