Decouple build process from packaging process

[thelovekesh]

Summary

Decoupled plugin zip process from the build process and update the packaging command in the workflow.

• On running npm run build:(dev|prod) it will execute the following according to NODE_ENV:

"build:dev": "cross-env NODE_ENV=development npm-run-all 'build:!(dev|prod)'",
"build:prod": "cross-env NODE_ENV=production npm-run-all 'build:!(dev|prod)'",
"build:prepare": "grunt clean",
"build:js": "wp-scripts build"

• On running npm run package:(dev|prod) it will execute the following commands:

"package:dev": "npm-run-all build:dev 'package:!(dev|prod)'",
"package:prod": "npm-run-all build:prod 'package:!(dev|prod)'",
"package:run": "grunt build",
"package:zip": "grunt create-build-zip"

Fixes #3302

Checklist

• My code is tested and passes existing tests.
• My code follows the Engineering Guidelines (updates are often made to the guidelines, check it out periodically).

[github-actions]

Plugin builds for 1862247 are ready 🛎️!

• Download development build
• Download production build

[milindmore22]

LGTM