Add yarn-plugin-conditions to update Babel 8 dependencies

[nicolo-ribaudo]

This is #12655, for some reason that PR wasn't in sync with my branch.

Q	A
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

This is a follow-up to #12440. In that PR I wrote

With this PR, it would be possible to inline many breaking changes (everything except for dependency updates) directly in main

but we would still need to use a next-8-dev branch for every change affecting package.json files, such as 5b3ca43. It's surely easier to merge/rebase than the complete next-8-dev branch we had before the BABEL_8_BREAKING flag, but it still requires some additional work.

With this PR, we can also start using the BABEL_8_BREAKING flag in package.json files, to move all the Babel 8 updates to main.

The yarn plugin source, if you are interested: https://github.com/nicolo-ribaudo/yarn-plugin-conditions

When CI of #12656 finishes, I'll post here the published package.json files so that you can see that the Yarn plugin works.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/37951/

[nicolo-ribaudo]

package.json published for @babel/cli in #12656's e2e tests:

{
  "name": "@babel/cli",
  "version": "7.12.13",
  "description": "Babel command line.",
  "author": "Sebastian McKenzie <sebmck@gmail.com>",
  "homepage": "https://babel.dev/docs/en/next/babel-cli",
  "bugs": "https://github.com/babel/babel/issues?utf8=%E2%9C%93&q=is%3Aissue+label%3A%22pkg%3A%20cli%22+is%3Aopen",
  "license": "MIT",
  "publishConfig": {
    "access": "public"
  },
  "repository": {
    "type": "git",
    "url": "https://github.com/babel/babel.git",
    "directory": "packages/babel-cli"
  },
  "keywords": [
    "6to5",
    "babel",
    "es6",
    "transpile",
    "transpiler",
    "babel-cli",
    "compiler"
  ],
  "dependencies": {
    "commander": "^4.0.1",
    "convert-source-map": "^1.1.0",
    "fs-readdir-recursive": "^1.1.0",
    "glob": "^7.0.0",
    "lodash": "^4.17.19",
    "make-dir": "^2.1.0",
    "slash": "^2.0.0",
    "source-map": "^0.5.0"
  },
  "optionalDependencies": {
    "@nicolo-ribaudo/chokidar-2": "2.1.8-no-fsevents",
    "chokidar": "^3.4.0"
  },
  "peerDependencies": {
    "@babel/core": "^7.0.0-0"
  },
  "devDependencies": {
    "@babel/core": "7.12.13",
    "@babel/helper-fixtures": "7.12.13",
    "rimraf": "^3.0.0"
  },
  "bin": {
    "babel": "./bin/babel.js",
    "babel-external-helpers": "./bin/babel-external-helpers.js"
  }
}

package.json published for @babel/cli in #12656's e2e-breaking tests: (note that the slash version changed)

{
  "name": "@babel/cli",
  "version": "7.12.13",
  "description": "Babel command line.",
  "author": "Sebastian McKenzie <sebmck@gmail.com>",
  "homepage": "https://babel.dev/docs/en/next/babel-cli",
  "bugs": "https://github.com/babel/babel/issues?utf8=%E2%9C%93&q=is%3Aissue+label%3A%22pkg%3A%20cli%22+is%3Aopen",
  "license": "MIT",
  "publishConfig": {
    "access": "public"
  },
  "repository": {
    "type": "git",
    "url": "https://github.com/babel/babel.git",
    "directory": "packages/babel-cli"
  },
  "keywords": [
    "6to5",
    "babel",
    "es6",
    "transpile",
    "transpiler",
    "babel-cli",
    "compiler"
  ],
  "dependencies": {
    "commander": "^4.0.1",
    "convert-source-map": "^1.1.0",
    "fs-readdir-recursive": "^1.1.0",
    "glob": "^7.0.0",
    "lodash": "^4.17.19",
    "make-dir": "^2.1.0",
    "slash": "^3.0.0",
    "source-map": "^0.5.0"
  },
  "optionalDependencies": {
    "@nicolo-ribaudo/chokidar-2": "2.1.8-no-fsevents",
    "chokidar": "^3.4.0"
  },
  "peerDependencies": {
    "@babel/core": "^7.0.0-0"
  },
  "devDependencies": {
    "@babel/core": "7.12.13",
    "@babel/helper-fixtures": "7.12.13",
    "rimraf": "^3.0.0"
  },
  "bin": {
    "babel": "./bin/babel.js",
    "babel-external-helpers": "./bin/babel-external-helpers.js"
  }
}

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