internal: use swc with ts-node (graphql#4457)

this currently requires a few changes to c8 control statements to ensure
complete code coverage presumably secondary to a bug/difference between
how tsc and swc handle source mapping

also: use --import with register script instead of --loader to silence
node.js warning regarding --loader

Author: yaacovCR

.mocharc.yml

@@ -4,4 +4,4 @@ check-leaks: true
 extension:
   - ts
 node-option:
-  - 'loader=ts-node/esm/transpile-only'
+  - 'import=./resources/register-ts-node.js'