haskell: switch to stack
this also means move testing/stack to community/stack
community/pandoc is updated to 2.19.2 because it's impossible to build binary 0.15.0 with ghc 9.0.2
also move hledger-ui and hledger-web to subpackages of hledger
todo: build stack with stack, for now it's built with cabal-stage0
closes #14120
Edited by Gay Pride