Chore: Mocha testing configuration (#23706)

.babelrc

.eslintignore

.eslintrc

.github/workflows/build_and_test.yml

.husky/pre-push

.mocharc.api.js

.mocharc.base.json

.mocharc.client.js

.mocharc.definition.js

.mocharc.js

app/apps/server/tests/messages.tests.js

app/custom-oauth/server/transform_helpers.tests.js

app/highlight-words/tests/helper.tests.js

app/lib/tests/server.tests.js

app/mailer/tests/api.spec.ts

app/markdown/tests/client.tests.js

app/mentions/tests/client.tests.js

app/mentions/tests/server.tests.js

app/meteor-accounts-saml/tests/server.tests.ts

app/models/server/raw/Sessions.tests.js