Add support for --only flag that matches lerna/pnpm run behavior

[jaredpalmer]

Add a new --only flag to support restricting task execution to only the tasks specified in run. This is to make it easier to adopt turbo in a Lerna codebase since --only behavior is effectively an exact match.

For this pipeline:

"turbo": {
    "pipeline": {
      "build": {
        "outputs": [
          "dist/**/*"
        ],
        "dependsOn": [
          "^build"
        ]
      },
      "test": {
        "dependsOn": [
          "^build"
        ]
      }
    }

turbo run test

turbo run test --only --graph

[vercel]

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