refactor(defaults): always set options, even if value hasn't changed (#26595)

Comparing against the old value before setting matched the original
C implementation, but there is no reason to use this restriction. In
particular, this inhibits using OptionSet to determine when the option
was set. If users need to handle a case where the option _changed_, it
is easy to do so in an OptionSet autocommand using v:option_new and
v:option_old (and friends).

runtime/lua/vim/_defaults.lua

@@ -189,9 +189,7 @@ if tty then
     -- Wait until Nvim is finished starting to set the option to ensure the
     -- OptionSet event fires.
     if vim.v.vim_did_enter == 1 then
-      if vim.o[option] ~= value then
-        vim.o[option] = value
-      end
+      vim.o[option] = value
     else
       vim.api.nvim_create_autocmd('VimEnter', {
         once = true,