luci-mod-status: transform status page Lua template into ucode template

Transform the only Lua template of the status module into an equivalent
ucode template and make it conditionally include the legacy Lua logic
factored out in a previous commit.

Only if the ucode Lua bridge is installed and loadable, the Lua template
loading the legacy Lua status partials is included.

After this commit, luci-mod-status is free of Lua dependencies.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>