feat(pack)!: use lazy.nvim

This commit replaces packer.nvim with lazy.nvim to make the lazy-load
based package management painless, with lazy.nvim's automatic module
lazy-loading and lockfile support.

Squashed commit of the following:

commit 4b972111b3f91f0b385a6d58640c7751ff8ecd22
Author: sefidel <contact@sefidel.net>
Date:   Sun Oct 1 20:43:42 2023 +0900

    wip: remove leftover mentions to packer.nvim

commit 536106e405b9ec20084b9735a937e80699cdcbb8
Author: sefidel <contact@sefidel.net>
Date:   Sun Oct 1 20:33:44 2023 +0900

    wip: get rid of luarocks macros

commit 6cf35948e4a3081446a9c9414bf350661444df72
Author: sefidel <contact@sefidel.net>
Date:   Sun Oct 1 20:18:51 2023 +0900

    wip: working lazy.nvim checkpoint

commit 407056efd6de976b4d91162c70e3b49cca17664e
Author: sefidel <contact@sefidel.net>
Date:   Sun Oct 1 13:38:43 2023 +0900

    wip: replace packer.nvim with lazy.nvim

1 files changed, 7 insertions, 3 deletions

diff --git a/init.lua b/init.lua
index 3e8e14b..82565b8 100644
--- a/init.lua
+++ b/init.lua
@@ -4,18 +4,22 @@ local run = vim.api.nvim_command
 -- Enable opt-in filetype.lua: https://github.com/neovim/neovim/pull/16600
 vim.g.do_filetype_lua = 1
 
+local ensure_paths = {}
+
 local function ensure(user, repo)
-  local install_path = fmt("%s/site/pack/packer/start/%s", vim.fn.stdpath("data"), repo)
+  local install_path = fmt("%s/lazy/%s", vim.fn.stdpath("data"), repo)
+  table.insert(ensure_paths, install_path)
   if vim.fn.empty(vim.fn.glob(install_path)) ~= 0 then
     print(fmt("Pack '%s' not found, cloning to %s", repo, install_path))
     run(fmt("!git clone https://github.com/%s/%s %s", user, repo, install_path))
-    run(fmt("packadd %s", repo))
   end
 end
 
-ensure("wbthomason", "packer.nvim")
+ensure("folke", "lazy.nvim")
 ensure("rktjmp", "hotpot.nvim")
 
+vim.opt.rtp:prepend(ensure_paths)
+
 require("hotpot").setup { provide_require_fennel = true }
 
 require("nvrc.ignite")