Expose delay link manager

[astrofrog]

This can be useful for other tools such as jdaviz

[codecov]

Codecov Report

Merging #2225 (da6693c) into master (3719c4f) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2225      +/-   ##
==========================================
- Coverage   88.07%   88.05%   -0.02%     
==========================================
  Files         247      247              
  Lines       23039    23168     +129     
==========================================
+ Hits        20291    20401     +110     
- Misses       2748     2767      +19     

Impacted Files	Coverage Δ
glue/core/data_collection.py	90.33% <100.00%> (-2.17%)	⬇️
glue/viewers/scatter/viewer.py	96.93% <0.00%> (-3.07%)	⬇️
glue/conftest.py	59.09% <0.00%> (-3.04%)	⬇️
glue/viewers/scatter/state.py	94.73% <0.00%> (-0.27%)	⬇️
glue/core/roi.py	91.68% <0.00%> (-0.24%)	⬇️
glue/viewers/scatter/layer_artist.py	97.21% <0.00%> (+0.01%)	⬆️
glue/viewers/scatter/python_export.py	97.72% <0.00%> (+0.16%)	⬆️
glue/viewers/scatter/qt/options_widget.py	93.42% <0.00%> (+0.99%)	⬆️
glue/core/util.py	73.68% <0.00%> (+1.66%)	⬆️
... and 1 more

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[pllim]

There is no docstring. Will this show up in API doc?

[astrofrog]

Added

[pllim]

Maybe another PR, but I think Glue could use a "performance tips and tricks" section like astropy. There are some things we could have done to speed things up but they are not intuitive.

[astrofrog]

@pllim - yes performance tricks would be a good idea - it's hard to anticipate all the bottlenecks in advance though and as this PR shows there was no public API before to solve this particular problem

[pllim]

LGTM!

[pllim]

p.s. Bonus would be an example code snippet showing the usage... but it does not block the merge of this PR.