test-performance build script: Add build:packages/wp-env start scripts as dependency

[strarsis]

Describe the bug
Just running the test-performance script (npm run test-performance) on a cleanly checked out worktree won't work as jest fails to find the monorepo modules in ./packages.
This can be easily solved by running the build:packages and wp-env start scripts to have the monorepo modules all built and loadable by jest.

To reproduce
Steps to reproduce the behavior:

1. Check out Gutenberg (e.g. git clone https://github.com/WordPress/gutenberg)`
2. Install the node modules/ensure node environment: nvm use && npm install
3. Run the test-performance script: npm run test-performance. Notice that jest fails to start the testing because it cannot find packages in the monorepo.
4. As fix, run the build:packages (npm run build:packages) and wp-env start (npm run wp-env start) scripts. After successful packages build, run the test-performance script again and notice that the jest loading issue is now fixed.

Expected behavior
When a npm package script is invoked, all scripts on which output/state modifications/installing the invoked script depends on, should run first.

[grappler]

Came across the same issue. It might be good to just document the fix in the documentation until it is correctly fixed.

[Mamaduka]

I will close this. The documentation has been updated via #41883. Props to @grappler.