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.

.changeset/fuzzy-cheetahs-approve.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/medusa": patch
+---
+
+feat(tests): harmonize and clean-up yarn test commands convention