Enable show short/full function names in Vv mode

[PeiweiHu]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've documented or updated the documentation of every function and struct this PR changes. If not so I've explained why.
• I've added tests that prove my fix is effective or that my feature works (if possible)
• I've updated the rizin book with the relevant information (if needed)

Detailed description

While trying to solve #1779, I found there already is an implementation to achieve this (not scroll but show the full name directly), which binds to [ and ]. This pr makes left and right arrows perform the same action as [ and ] and appends help info.

IMO this is more useful than scrolling the selected function name since it can show full names of many functions at the same time. The implementation that scrolls the selected function name seems less meaningful since when you select it, the right panel (i.e., pdf in the following pics) already shows the function with its name.

Test plan

...

Closing issues

closes #1779