feat(api): nvim_set_option_value(operation=...) #39849

Problem:
`nvim_set_option_value` cannot "update" options similar to `:set opt=`,
`:set opt+=`, etc. The Lua impls of "vim.opt" / "vim.o" have incomplete,
bespoke reimplementations of those operations.

ref #38420

Solution:
- Add `operation` param to `nvim_set_option_value`, which may be "set",
  "append", "prepend", or "remove".
- Use this feature to implement `vim.opt` / `vim.o`.

runtime/lua/vim/_meta/api_keysets.gen.lua

@@ -381,7 +381,9 @@ error('Cannot require a meta file')
 
 --- @class vim.api.keyset.option
 --- @field buf? integer
+--- @field dry_run? boolean
 --- @field filetype? string
+--- @field operation? string
 --- @field scope? string
 --- @field tab? integer
 --- @field win? integer