Add force-sync command to ntp-ctl

[rnijveld]

This builds on top of #1508 which should probably be looked at first. I've made a couple of items public in implementing this. I think we could reduce the amount of duplicated code a little more by restructuring a little more, but I wanted to get a quick example of this utility as soon as possible. The source spawning currently happens in serial, but this could be made to be in parallel as well, but I don't think this tool needs to be that performant though. I wonder if we still would want to add a little more interactivity to this as well, just so users understand that this bypasses most safety checks. This fixes #1494.

[codecov]

Codecov Report

Attention: Patch coverage is 17.52137% with 193 lines in your changes missing coverage. Please review.

Project coverage is 81.73%. Comparing base (d3765d9) to head (3e81437).

Files	Patch %	Lines
ntpd/src/ctl/force_sync.rs	0.00%	177 Missing ⚠️
ntp-proto/src/source.rs	63.33%	11 Missing ⚠️
ntpd/src/ctl/mod.rs	16.66%	5 Missing ⚠️

Additional details and impacted files

@@                      Coverage Diff                      @@
##           remove-non-basic-spawners    #1512      +/-   ##
=============================================================
- Coverage                      82.50%   81.73%   -0.78%     
=============================================================
  Files                             62       63       +1     
  Lines                          18758    18962     +204     
=============================================================
+ Hits                           15476    15498      +22     
- Misses                          3282     3464     +182     

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[davidv1992]

@rnijveld needs rebase