build: remove typescript 3.6 and 3.7 support (#36329)

Remove TypeScript 3.6 and 3.7 support from Angular along with tests that
ensure those TS versions work.

BREAKING CHANGE: typescript 3.6 and 3.7 are no longer supported, please
update to typescript 3.8

PR Close #36329

packages/compiler-cli/package.json

@@ -27,7 +27,7 @@
   "peerDependencies": {
     "@angular/compiler": "0.0.0-PLACEHOLDER",
     "tslib": "^1.10.0",
-    "typescript": ">=3.6 <3.9"
+    "typescript": ">=3.8 <3.9"
   },
   "engines": {
     "node": ">=10.0"
@@ -52,4 +52,4 @@
   "publishConfig": {
     "registry": "https://wombat-dressing-room.appspot.com"
   }
-}
+}

packages/compiler-cli/src/typescript_support.ts

@@ -12,7 +12,7 @@ import {compareVersions} from './diagnostics/typescript_version';
  * Minimum supported TypeScript version
  * ∀ supported typescript version v, v >= MIN_TS_VERSION
  */
-const MIN_TS_VERSION = '3.6.4';
+const MIN_TS_VERSION = '3.8.3';
 
 /**
  * Supremum of supported TypeScript versions