Update v7 branch to use Yarn v2 and improve CI process

[markerikson]

This PR:

• Does the same switch from NPM to Yarn v2 that I did in Convert package management to Yarn v2 #1751 for the TS migration
• Does the same updates to our CI process that I did in Improve CI setup #1752

This gives us consistency in build steps and package management between the 7.x and master / 8.x branches

[github-actions]

Size Change: 0 B

Total Size: 26.7 kB

ℹ️ View Unchanged

Filename	Size	Change
dist/react-redux.js	21.4 kB	0 B
dist/react-redux.min.js	5.24 kB	0 B

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