feat: shard modules and API integration tests (#6775)

what:

- runs module and api integration tests in matrix strategy
  - v28 of jest comes with sharding support, which we can utilize when we upgrade
- splits the tests by number of matrix jobs and run them in parallel
  - This introduced some flakiness in some specs, but couldn't reproduce locally. Those have been skipped for now.
- uses swc/jest for added performance
  - Locally, a chunk took 90 seconds with babel and 30 seconds with swc. 
  - This translated to 2 mins saved per shard in CI, but haven't tested this enough.

integration-tests/api/package.json

@@ -6,6 +6,7 @@
   "private": true,
   "scripts": {
     "test:integration": "jest --silent --maxWorkers=50% --bail --detectOpenHandles --forceExit --logHeapUsage",
+    "test:integration:chunk": "jest --silent --bail --maxWorkers=50% --forceExit --testPathPattern=$(echo $CHUNKS | jq -r \".[${CHUNK}] | .[]\")",
     "build": "babel src -d dist --extensions \".ts,.js\""
   },
   "dependencies": {
@@ -37,6 +38,8 @@
     "@babel/cli": "^7.12.10",
     "@babel/core": "^7.12.10",
     "@babel/node": "^7.12.10",
+    "@swc/core": "^1.4.8",
+    "@swc/jest": "^0.2.36",
     "babel-preset-medusa-package": "*",
     "jest": "^26.6.3",
     "jest-environment-node": "26.6.2"