:middleware pt 2

[borkdude]

• still have doubts about converting handler -> xform - this complicates referencing other "handler" vars because they'll be converted to xform first and the var is lost when converting from handler -> xform. maybe we should revert the xform approach to the cider nREPL approach instead (this will be a breaking change of babashka.nrepl users of which there aren't that many currently) or we should support passing xforms by users
• what is passed around is :ctx :msg :opts but this from a babashka user perspective not what we want: we certainly don't want to see the ctx, but just the msg
• is CIDER nREPL compatibility a concern, i.e. do we want to load that "as is" at some point, or do we want to have bespoke babashka nREPL middleware? seems like a bit of a waste of effort?
• still need to support strings in :requires and :expects like cider nREPL does so we don't have to refer to internal vars directly

[borkdude]

cc @phronmophobic @benjamin-asdf