[flang][fir] Add remaining Ops. Updates to pre-existing Ops.

  - add ops: rebox, insert_on_range, absent, is_present
  - embox, coordinate_of: replace old hand-written parser/pretty-printer with assembly format
  - remove dead floating point ops, since buitlins work for all types
  - update call op
  - update documentation
  - misc. NFC to formatting
  - add op round trip tests

Authors: Eric Schweitz, Jean Perier, Zachary Selk, Kiran Chandramohan, et.al.

Differential Revision: https://reviews.llvm.org/D97500