build: move all generator scripts to src/gen/

- Move all generator Lua scripts to the `src/gen/`
- Add a `.luarc.json` to `src/gen/`
- Add a `preload.lua` to `src/gen/`
  - Add `src` to `package.path` so it aligns with `.luarc.json'
- Fix all `require` statements in `src/gen/` so they are consistent:
    - `require('scripts.foo')` -> `require('gen.foo')`
    - `require('src.nvim.options')` -> `require('nvim.options')`
    - `require('api.dispatch_deprecated')` -> `require('nvim.api.dispatch_deprecated')`

test/.luarc.json

@@ -6,6 +6,7 @@
   "workspace": {
     "library": [
       "../runtime/lua",
+      "../src",
       "../build/usr/share/lua/5.1",
       "../build",
       "${3rd}/busted/library",

test/functional/script/luacats_grammar_spec.lua

@@ -2,7 +2,7 @@ local t = require('test.testutil')
 
 local eq = t.eq
 
-local grammar = require('scripts/luacats_grammar')
+local grammar = require('gen.luacats_grammar')
 
 describe('luacats grammar', function()
   --- @param text string

test/functional/script/luacats_parser_spec.lua

@@ -2,7 +2,7 @@ local t = require('test.testutil')
 
 local eq = t.eq
 
-local parser = require('scripts/luacats_parser')
+local parser = require('gen.luacats_parser')
 
 --- @param name string
 --- @param text string

test/functional/script/text_utils_spec.lua

@@ -11,7 +11,7 @@ local function md_to_vimdoc(text, start_indent, indent, text_width)
     start_indent = start_indent or 0
     indent = indent or 0
     text_width = text_width or 70
-    local util = require('scripts/util')
+    local util = require('src/gen/util')
     return util.md_to_vimdoc(table.concat(text, '\n'), start_indent, indent, text_width)
   ]],
     text,

test/lua_runner.lua

@@ -2,10 +2,8 @@ local platform = vim.uv.os_uname()
 local deps_install_dir = table.remove(_G.arg, 1)
 local subcommand = table.remove(_G.arg, 1)
 local suffix = (platform and platform.sysname:lower():find 'windows') and '.dll' or '.so'
-package.path = deps_install_dir
-  .. '/share/lua/5.1/?.lua;'
-  .. deps_install_dir
-  .. '/share/lua/5.1/?/init.lua;'
+package.path = (deps_install_dir .. '/share/lua/5.1/?.lua;')
+  .. (deps_install_dir .. '/share/lua/5.1/?/init.lua;')
   .. package.path
 package.cpath = deps_install_dir .. '/lib/lua/5.1/?' .. suffix .. ';' .. package.cpath