Move `glibc-function-args` to GEF-Extras

[hugsy]

Description/Motivation/Screenshots

This PR moves the old mechanism to print out the glibc function parameter names from GEF to GEF-Extras. This PR also registers it as a conditional external context pane, which will only display is we hit a call instruction.

See

• https://github.com/hugsy/gef/pull/866
• https://github.com/hugsy/gef/issues/865

How Has This Been Tested ?

"Tested" indicates that the PR works and the unit test (i.e. make test) run passes without issue.

• [x] x86-32
• [x] x86-64
• [ ] ARM
• [ ] AARCH64
• [ ] MIPS
• [ ] POWERPC
• [ ] SPARC
• [ ] RISC-V

Checklist

• [x] My PR was done against the dev branch, not main.
• [x] My code follows the code style of this project.
• [x] My change includes a change to the documentation, if required.
• [ ] If my change adds new code, adequate tests have been added.
• [x] I have read and agree to the CONTRIBUTING document.