Segments: Add segment querying utils, refactoring

This merge request is focused on adding utilties and refactoring for segment-related logic:

Python API

• Move common segments utils to segments module (segutil -> segments)
  • Utilities for generating job segment boundaries (originally part of inspiral_pipe.py)
• Add new utilities
  • Query science/veto segments from DQSegDB and GWOSC
  • Note: some of this exists in standalone scripts in various places

Programs

• Add gstlal_query_(gwosc/dqsegdb)_segments
  • Get science segments from GWOSC/DQSegDB with similar CLI
  • Leverages functions from gstlal.segments
• Add gstlal_query_(gwosc/dqsegdb)_veto_segments
  • Get vetoes from GWOSC/DQSegDB with similar CLI
  • Leverages functions from gstlal.segments
  • For GWOSC, scripts existed for this for O2. generalize for all runs
  • For DQSegDB, we currently rely on ligolw_segments_from_cats_dqsegdb
    • Scripts not been ported to python3, unclear if script sees any usage beyond GstLAL
    • No python API analog to this without depending on gwpy

Update: removed the I/O segments utilities