Add developer "productivity" features

Problem to solve

Developers using GitLab as their platform may need both tactical and strategic view on their work and work plans. Typically that entails:

• listing todos that are within current scope (milestone, timeframe, labels)
• listing MRs to review that are within current scope (milestone, timeframe, labels)
• listing MRs in development that are within current scope (milestone, timeframe, labels)
• listing issues that are within current scope (milestone, timeframe, labels)
• listing work don within specified period of time (within the scope of milestone, labels)

Proposal

• expand existing commands to allow finer filtering of output:
  • mr list
  • issue list
• add new commands (with extended filtering)
  • event list
  • todo list
• un-paginate results for all involved commands.

all of the above commands should produce both text and json outputs to allow for immediate display or further processing of results.

Further details

Typical questions developer asks (sample scoping applied):

• What needs to be reviewed for the next milestone?
• Which of my MRs need to be completed for the next milestone?
• What issues need resolution for the next milestone?
• What did I work on past week?

Most of those answers we already have in GitLab but not readily available and it is cumbersome to extract them efficiently and track them. Having simplified view of "tactical" (what needs to be done for the milestone) vs "strategic" (what work is assigned to me) vs historical (what work have I done) helps with time management and planning.

Links / references