Docs: Update PR workflow documentation

[alamb]

Which issue does this PR close?

Part of #7013

Rationale for this change

I realize I often wait some time between approve and merge which can be confusing and is not really documented. Most recently this came up with @shanretoo on #10476 at #10476 (comment)

What changes are included in this PR?

Clarify documentation explaining the PR cycle

Are these changes tested?

Are there any user-facing changes?

[comphead]

lgtm, thanks @alamb
I'm thinking should describe a draft status usage as well?

My vision the PR should be in draft in some scenarios:

• Waiting too long(how long?) for the author response on feedbacks
• if the PR is POC, WIP, or other conditions when PR is not really to be reviewed

[viirya]

I realize I often wait some time between approve and merge which can be confusing and is not really documented. Most recently this came up with @shanretoo on #10476 at #10476 (comment)

Took a look. I think this only happens in rare case? The contributor is not only a new contributor to DataFusion but looks like has not participated in open source before (since the GitHub account is created recently).

For such cases, I wonder if they will look at the document added here firstly. 😄

[alamb]

I plan to incorporate the feedback on this PR, I just haven't had a chance yet. I hope to do so over the next few days

[alamb]

For such cases, I wonder if they will look at the document added here firstly. 😄

This is an excellent point @viirya -- I realize some people may not read the doc, but at least now we will have a place to point them

[alamb]

I'm thinking should describe a draft status usage as well?

@comphead -- in so far that we know how we use the draft status, that might be helpful. However, I am not sure it is consistently used enough to explain it.

[alamb]

I also added two links to github filters I use to find PRs waiting on review and PRs that are approved waiting on merge:

Thank you all for the comments. I'll merge this one in and we can address additional comments / suggestions as follow on PRs