Document pub workspaces

[sigurdm]

Fixes #5891

Should probably only land with 3.6

[dart-github-bot]

Visit the preview URL for this PR (updated for commit fc13a5f):

https://dart-dev--pr6117-document-workspaces-r9fkahhq.web.app

[MaryaBelanger]

I'm not sure what the issue with the tests is, but I get the same thing locally. Maybe @parlough can help?

Edit: Yeah, I see he made a possibly similar fix earlier in this pr. I'm not sure what he did there and I don't want to mess anything up, so we'll wait for that and then merge this!

[MaryaBelanger]

Thanks so much @parlough!

I just noticed it says "should only be merged with 3.6", so I won't merge it now.

[MaryaBelanger]

typos

[MaryaBelanger]

@sigurdm I added d017546 to "close the loop" about analysis contexts, since you mentioned that without workspaces, analysis contexts cause performance issues. So I added a quick line to to confirm that with workspaces, analysis performance will improve.

The link on analysis context will land with #6239

Edit: I actually ended up undoing all of this and removing the mention of analysis context based on Brian's comment here, I think that makes much more sense.

[sigurdm]

I made an extension to this PR in sigurdm#1. That should probably only land if we get dart-lang/sdk#59650 cherry picked.

[MaryaBelanger]

@parlough Since you've been working on moving things out from under /guides, where do you suggest we place this new page?