Use @swc/jest to speed up tests

[richrace]

• Unit tests
• Integration tests
• Tweak the npm run tests config
• Cache node modules properly in CircleCI properly

On Circle CI:

Main:

• Total time of job for unit tests = 1min 40s
• Unit tests = 32s
• Total time of job for integration tests = 4m 29s
• Integration tests = 1m

This branch (with cached npm modules):

• Total time of job for unit tests = 31s
• Unit tests = 4s
• Total time of job for integration tests = 1m 55s
• Integration tests = 39s