Split test into a separate workspace to cleanup package.json.

[mshima]

There are a lot of overrides in package.json to allow testing old generators.

environment/package.json

Lines 122 to 186 in 9d23482

	"overrides": {
	"yeoman-generator-2": {
	"chalk": "^4.1.0",
	"dargs": "^7.0.0",
	"debug": "^4.1.1",
	"execa": "^5.1.1",
	"github-username": "^6.0.0",
	"lodash": "^4.17.11",
	"mem-fs-editor": "^9.0.0",
	"minimist": "^1.2.5",
	"pacote": "^15.2.0",
	"read-pkg-up": "^7.0.1",
	"run-async": "^2.0.0",
	"semver": "^7.2.1",
	"shelljs": "^0.8.5",
	"sort-keys": "^4.2.0",
	"text-table": "^0.2.0",
	"yeoman-environment": "file:./"
	},
	"yeoman-generator-4": {
	"chalk": "^4.1.0",
	"dargs": "^7.0.0",
	"debug": "^4.1.1",
	"execa": "^5.1.1",
	"github-username": "^6.0.0",
	"lodash": "^4.17.11",
	"mem-fs-editor": "^9.0.0",
	"minimist": "^1.2.5",
	"pacote": "^15.2.0",
	"read-pkg-up": "^7.0.1",
	"run-async": "^2.0.0",
	"semver": "^7.2.1",
	"shelljs": "^0.8.5",
	"sort-keys": "^4.2.0",
	"text-table": "^0.2.0",
	"yeoman-environment": "file:./"
	},
	"yeoman-generator-5": {
	"chalk": "^4.1.0",
	"dargs": "^7.0.0",
	"debug": "^4.1.1",
	"execa": "^5.1.1",
	"github-username": "^6.0.0",
	"lodash": "^4.17.11",
	"mem-fs-editor": "^9.0.0",
	"minimist": "^1.2.5",
	"pacote": "^15.2.0",
	"read-pkg-up": "^7.0.1",
	"run-async": "^2.0.0",
	"semver": "^7.2.1",
	"shelljs": "^0.8.5",
	"sort-keys": "^4.2.0",
	"text-table": "^0.2.0",
	"yeoman-environment": "file:./"
	},
	"yeoman-generator-6": {
	"yeoman-environment": "file:./"
	},
	"yeoman-generator-7": {
	"yeoman-environment": "file:./"
	},
	"yeoman-generator-8": {
	"yeoman-environment": "file:./"
	}
	}

We should move those tests to a separate workspace to cleanup main package.json.

[mshima]

@UlisesGascon @JoshuaKGoldberg my experience in monorepo is not good, maybe you can help with this.