Lua stdlib: string.buffer, table.clear

[justinmk]

Problem

We have internal shims for luajit features:

require('string.buffer')
require('table.clear')
require('table.new')

ref #39222

Expected behavior

Document and expose these for use by plugins.
Assuming there is no risk of forward incompatibility.

Note

• Lua 5.5 has a table.create, which is similar to require('table.new'), but still lacks require('table.clear')

[mfussenegger]

We have plans to add other things there too such as table.pack

My vote would go towards putting these things under the vim namespace instead of monkey patching table. For people switching between Neovim luadev and other Lua projects, it's confusing if Lua stdlib components have methods that aren't part of Lua5.1 or LuaJit.