Use more nodelike paths for import types when possible (#24610)

* Use more nodelike paths for import types when possible

* move functionality from services into compiler, fix with propert file/directory conflict handling

* mark suspect cast

src/compiler/moduleNameResolver.ts

@@ -132,10 +132,6 @@ namespace ts {
         }
     }
 
-    export interface GetEffectiveTypeRootsHost {
-        directoryExists?(directoryName: string): boolean;
-        getCurrentDirectory?(): string;
-    }
     export function getEffectiveTypeRoots(options: CompilerOptions, host: GetEffectiveTypeRootsHost): string[] | undefined {
         if (options.typeRoots) {
             return options.typeRoots;