refactor(Commands): Merge all commands into one :Obsidian command

[jblsp]

This "namespaces" all of the commands as discussed here.

I accidentally closed the old PR, this is the one from before but with some changes to the command registering and it adds an option to enable all of the old commands.

[neo451]

thank you for your work, this looks amazing 👍
I have no issue merging this but looks like a big change that can break people's configs, the legacy commands approach is very nice indeed, I wonder @guspix @ffricken thinks
Plus, there's a few places in utils.lua and mappings.lua that uses the old command string, also the gf_passthrough in the README also need to change