1. Follows advice from
https://sol2.readthedocs.io/en/latest/functions.html to use
`set_function` when binding functions.
2. Adds autocomplete support for userdata methods.
3. Simplifies property bindings and improves string handling.
Also renames lua/lua.hpp to lua/lua_global.hpp.
The previous name broke version auto-detection in sol2, which involves
calling `__has_include(<lua/lua.hpp>)`.
Fully migrates debug commands to Lua and organizes them into logical
groups.
The CLI `+` syntax now runs Lua, e.g.:
```bash
build/devilutionx '+dev.player.trn.plr("infra")'
```
Chat hotkeys run Lua code if they start with `/lua`, e.g.:
```ini
[NetMsg]
QuickMessage1=/lua message(dev.player.info())
```
Gleb Mazovetskiy