feat(tests): harmonize and clean-up yarn test commands convention (#3695)

## What

Harmonize and clean-up yarn test commands convention.

## Why

Current strategy to filter integration tests from unit tests was cumbersome to maintain. Also, some packages declared `test:unit` which ended up being an alias to `test`.

## How

* Remove all occurrences of `test:unit`
* Rename all `test` commands under `/integration-tests/**/package.json` to `test:integration`
* In the root `package.json`, rewrite `test:integration` command to run `turbo run test:integration`
* In the root `package.json`, remove filtering on the `test` command
* Introduce a new `test:integration` task in the Turborepo config.

integration-tests/package.json

@@ -5,7 +5,7 @@
   "main": "jest.config.js",
   "private": true,
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test:integration": "echo \"Error: no test specified\" && exit 1"
   },
   "author": "Zakaria S. El Asri",
   "license": "ISC",