Add new help categories to remove parentheses (context) from help texts

[Niloth-p]

What does this PR do, and why?

Adds the following new help categories to remove the corresponding context-suffixes (in parentheses) from help texts:

• Stream information ("from stream information" suffixes)
• Message information ("from message information" suffixes)
• User list actions ("from user list" suffixes)

That removes parantheses from all the help texts.

Each of the categories are added in their own commit, for readability. A new command entry NARROW_TO_USER_PM is also added to the user list actions.

Outstanding aspect(s)

This PR is about removing the contexts mentioned in parentheses as suffixes. And it removes all of them. But, it also introduces new parentheses for the help category names itself.

I went with this because

1. There is not much repetition of the content in the parentheses
2. Length constraints apply to help texts, they don't wrap. But, help category names do wrap.
3. They add some needed clarity, on when/where the help category's hotkeys will work.

Feedback welcome!

External discussion & connections

• [x] Discussed in #zulip-terminal in re-categorize
• [ ] Fully fixes #
• [ ] Partially fixes issue #
• [ ] Builds upon previous unmerged work in PR #
• [ ] Is a follow-up to work in PR #
• [ ] Requires merge of PR #
• [ ] Merge will enable work on #

How did you test this?

• [ ] Manually - Behavioral changes
• [x] Manually - Visual changes
• [ ] Adapting existing automated tests
• [ ] Adding automated tests for new behavior (or missing tests)
• [x] Existing automated tests should already cover this (only a refactor of tested code)

Self-review checklist for each commit

• [x] It is a minimal coherent idea
• [x] It has a commit summary following the documented style (title & body)
• [x] It has a commit summary describing the motivation and reasoning for the change
• [x] It individually passes linting and tests
• [ ] It contains test additions for any new behavior
• [x] It flows clearly from a previous branch commit, and/or prepares for the next commit

Visual changes

The information popup categories: The user list actions category:

[Niloth-p]

Rebased onto main, added a comment as per feedback.

[Niloth-p]

Rebased and pushed.

We just have 2 keys for the 2 categories 'Stream message info actions' and 'User list actions'. As discussed, those make it tiny categories. So,

• we could either discuss the alternative options that I previously suggested in the CZO topic,
• or leave this PR until more hotkeys are added to these categories,
• or we could push these changes but put these tiny categories at the bottom of the help menu.

[neiljp]

@Niloth-p Merging this now; thanks for the earlier review zormit :+1:

My main concern is the location of the resulting extra categories (and their size, as discussed before), but I think this does read more cleanly :)