Use `yarn workspaces list` to prefilter any subfolders that are covered by the single yarn workspace

[mrzarquon]

We made need some more advanced logic for yarn, where we:

• check for yarn.lock files
• get list of subfolders covered by those yarn.lock directories
• exclude executing on those folders or including them in any other node language detection downstream

[scott-es]

Will be addressed by https://github.com/snyk-tech-services/snyk-bulk/pull/47

[scott-es]

merged