Cache parsed path mapping patterns (#44078)

* Cache parsed path mapping patterns

If a project has many of them (e.g. 1800), parsing the patterns
repeatedly can take up a lot of time.

* Move cache to ConfigFileSpecs

* Inline constants

* Simplify cache access

src/compiler/types.ts

@@ -6195,6 +6195,7 @@ namespace ts {
         validatedFilesSpec: readonly string[] | undefined;
         validatedIncludeSpecs: readonly string[] | undefined;
         validatedExcludeSpecs: readonly string[] | undefined;
+        pathPatterns: readonly (string | Pattern)[] | undefined;
     }
 
     /* @internal */