hg.sr.ht: overhaul init files

Deploy hg.sr.ht's partial config files

hg.sr.ht: set arch to all

hg.sr.ht: build hgsrht-keys Go program

Add mercurial evolve package, make it a dependency of hgsrht

hg.sr.ht: normalize init scripts

Add hg.sr.ht-webhooks service

Add hg.sr.ht package