Speed up building extensionForTesting

[kaklakariada]

EM uses extensionForTesting as an extension in integration tests. This extension is written in typescript. The extension is a template with placeholders. Each test does the following steps:

1. It fills the placeholders
2. Writes the extension TS file to a temp folder
3. Runs npm run build which
   1. Runs TypeScript compiler tsc
   2. Bundles the JS to a single file using esbuild

We can speedup this process by converting the extension file to pure JavaScript, thus saving the tsc step.

Disadvantage of this change: The extensionForTesting is not type-checked against the extension-manager-interface.

Test results

• Test 1: time go test ./... -p 1 -count 1 -v with DB already running
• Test 2: Just run controller_test.go from IDE. This test uses extensionForTesting very often

Original TypeScript

• Test 1:

  real    3m53.037s
  user    4m34.663s
  sys     0m22.817s

• Test 2: 77.253s

Pure JavaScript

• Test 1:

  real    2m5.757s
  user    0m47.852s
  sys     0m12.047s

• Test 2: 18.944s