Fix: (#5816) Trailing slash breaks workspace

[sfsr12]

Summary
This fixes #5816 for both types of failure described. Both if the pattern starts with ./ or ends with /

With the silent nature of the failure, it makes it difficult to notice. This will prevent the issue.
Also, if you "yarn add" anything to the workspaces a yarn.lock is created and node_modules are installed at the workspace level.

Test plan

Simply create a package that includes workspaces. If you use a pattern that starts with ./ or ends with / you will get the following message when you try to run workspace functions from any directory besides the workspace root.

> yarn workspaces info
error Cannot find the root of your workspace - are you sure you're currently in a workspace?
info Visit https://yarnpkg.com/en/docs/cli/workspaces for documentation about this command.

After this change you get proper output

> yarn workspaces info
{
  "workspace-a": {
    "location": "packages/workspace-a",
    "workspaceDependencies": [],
    "mismatchedWorkspaceDependencies": []
  },
  "workspace-b": {
    "location": "packages/workspace-b",
    "workspaceDependencies": [
      "workspace-a"
    ],
    "mismatchedWorkspaceDependencies": []
  },
  "yarn": {
    "location": "packages/yarnsfsr",
    "workspaceDependencies": [],
    "mismatchedWorkspaceDependencies": []
  }
}

[sfsr12]

Never done this before - so not sure if I did something wrong.

It is saying it fails various tests - but I don't think that is related to my code.

Any help would be appreciated.

Thanks