chore: make TypeScript strict in test folder. Simplify tsconfig (#10582)

This PR makes the "test" folder strict in typescript.

`pnpm build:test` before: Found 3275 errors in 174 files.
`pnpm build:test` after: Found 4912 errors in 268 files.

At some point we should bring that number to 0 and make it a requirement
in the CI. Currently `pnpm build:test` is not run anywhere in the CI.

Additionally, I took the opportunity to combine the duplicate
configurations from `tsconfig.json` and `tsconfig.typecheck.json` using
"extend".

declaration, declarationMap and sourceMap have been removed as they have
no reason to exist in noEmit.

The settings I left in `tsconfig.typecheck.json` are ones that I'm not
sure why they are there. Perhaps the file could be removed or at least
reduced further.

test/types/tsconfig.json

@@ -1,8 +1,3 @@
 {
-  "extends": "../tsconfig.json",
-  "compilerOptions": {
-    "strict": true,
-    "exactOptionalPropertyTypes": true,
-    "noUncheckedIndexedAccess": true
-  }
+  "extends": "../tsconfig.json"
 }