(optim): no need for separate cacheRoot per format

- similarly to the previous commit, it's unnecessary and less
  performant to have a separate cacheRoot per format
  - each TS compilation occurs before the format is changed anyway, so
    at that point in the process, format is irrelevant
  - builds can now re-use cache from other formats, which resulted in
    a perf boost during testing

src/createRollupConfig.ts

@@ -146,7 +146,6 @@ export async function createRollupConfig(
       },
       typescript({
         typescript: ts,
-        cacheRoot: `./node_modules/.cache/tsdx/${opts.format}/`,
         tsconfig: opts.tsconfig,
         tsconfigDefaults: {
           exclude: [