docs(events): Lua types for autocmd event-data #38518

Problem:
  No LuaLS types for event-data fields (ev.data). Types are only
  documented ad hoc in scattered locations.

Solution:
  Add runtime/lua/vim/_meta/events.lua defining vim.event.<name>.data
  classes for events that provide ev.data. Reference the types from
  each event's help in autocmd.txt, lsp.txt, and pack.txt.

runtime/lua/vim/_meta/events.lua

@@ -0,0 +1,56 @@
+--- @meta
+error('Cannot require a meta file')
+
+--- @class vim.event.lspattach.data
+--- @field client_id integer
+
+--- @class vim.event.lspdetach.data
+--- @field client_id integer
+
+--- @class vim.event.lspnotify.data
+--- @field client_id integer
+--- @field method string
+--- @field params table
+
+--- @class vim.event.lspprogress.data
+--- @field client_id integer
+--- @field params lsp.ProgressParams
+
+--- @class vim.event.lsprequest.data
+--- @field client_id integer
+--- @field request_id integer
+--- @field request table
+
+--- @class vim.event.lsptokenupdate.data
+--- @field client_id integer
+--- @field token table
+
+--- @class vim.event.markset.data
+--- @field name string
+--- @field line integer
+--- @field col integer
+
+--- @class vim.event.packchanged.data
+--- @field active boolean
+--- @field kind string
+--- @field spec vim.pack.Spec
+--- @field path string
+
+--- @class vim.event.packchangedpre.data : vim.event.packchanged.data
+
+--- @class vim.event.progress.data
+--- @field id any
+--- @field text string[]
+--- @field data? table
+--- @field percent? integer
+--- @field source? string
+--- @field status? string
+--- @field title? string
+
+--- @class vim.event.termrequest.data
+--- @field sequence string
+--- @field terminator string
+--- @field cursor integer[]
+
+--- @class vim.event.termresponse.data
+--- @field sequence string

runtime/lua/vim/pack.lua

@@ -175,6 +175,8 @@
 ---- `spec` - plugin's specification with defaults made explicit.
 ---- `path` - full path to plugin's directory.
 ---
+---See `vim.event.packchanged.data` and `vim.event.packchangedpre.data`.
+---
 --- These events can be used to execute plugin hooks. For example:
 ---```lua
 ---local hooks = function(ev)