feat(rockspec): fallback to root manifest when building w/ rockspec

[cosmicboots]

Description

This PR adds the rocks server root manifest as an extra fallback when building plugins with luarocks. If a plugin specifies dependencies that aren't found in the luarocks dev manifest, the local build will fail due to missing dependencies.

For example, dbus_proxy isn't present in the luarocks dev manifests (thus doesn't appear in search):

lazy.nvim via 🌙 v5.4.8
❯ luarocks --lua-version 5.1 search dbus_proxy

dbus_proxy - Search results for Lua 5.1:
========================================


Rockspecs and source rocks:
---------------------------

dbus_proxy
   0.10.4-1 (rockspec) - https://luarocks.org
   0.10.4-1 (src) - https://luarocks.org
   0.10.3-2 (rockspec) - https://luarocks.org
   0.10.3-2 (src) - https://luarocks.org
   0.10.2-1 (rockspec) - https://luarocks.org
   0.10.2-1 (src) - https://luarocks.org
   0.10.0-1 (rockspec) - https://luarocks.org
   0.10.0-1 (src) - https://luarocks.org
   0.9.0-1 (rockspec) - https://luarocks.org
   0.8.5-1 (rockspec) - https://luarocks.org
   0.8.1-1 (rockspec) - https://luarocks.org
   0.8.0-1 (rockspec) - https://luarocks.org
   0.7.1-1 (rockspec) - https://luarocks.org
   0.7.0-1 (rockspec) - https://luarocks.org

lazy.nvim via 🌙 v5.4.8
❯ luarocks --lua-version 5.1 search --dev dbus_proxy

dbus_proxy - Search results for Lua 5.1:
========================================

Related Issue(s)

Not directly a lazy.nvim issue, but this popped up from an issue with one of my small plugins: cosmicboots/system-theme.nvim#1.