Install AstroNvim dependencies on devserver role

Improve developer experience by switching from the
abandoned SpaceVim setup to modern Lazy.nvim ecosystem,
with a recommendation to use AstroNvim.

Install bottom, gdu, lazygit, tree-sitter, universal ctags.

On FreeBSD, gdu conflicts with coreutils du, so install it
at /opt/gdu/gdu. Pending a solution upstream to set the binary
path, add a fix_gdu devserver homefiles task to get a symlink
to ~/bin, and show with an example for my profile how to make
that directory take precedence over /usr/local/bin.

Ref T295

Test Plan:

• Run AstroNvim diagnostics
• generate tags for rOPS and ctrl + click a word
• <space>tu for gdu fix

Differential Revision: https://devcentral.nasqueron.org/D4214