StateTimeline: Add disconnect value option

[drew08t]

What this PR does / why we need it:
Currently in state timeline, a user has the option to connect all null values or null values within a certain threshold of time range. Users do not however have the ability to disconnect non-null values that are outside of a time range from each other. This adds the option for users to disconnect non-null values that are outside of a threshold of time range.

• Render blank time range up to cut-off time, not just the threshold time (yellow region in image below should be completely removed, instead it is partially rendered for time range equal to the threshold)
  This will be addressed in separate issues: StateTimeline: Remove GraphNG component in favor of direct implementation of UPlotChart #71245 + StateTimeline: Add gradient to value disconnect #71236

Closes #70285

[leeoniya]

sure, why not 😅

however, i would expect this to work differently with our default-on setting of "Merge equal consecutive values". e.g. the two consecutive green "a" states should be merged before this disconnect threshold is applied. currently not easy to get this working since disconnect happens first in the data while mergeValues happens later in the renderer. we may need to move the merging behavior into the data as well.

[leeoniya]

never mind the above comment, i think it's working as expected in that case. i did find some other weirdness to check out in a follow-up tho. notice how the rendering changes at the end with > 17m threshold:

http://localhost:3000/d/mIJjFy8Gz/timeline-modes?orgId=1&editPanel=9

Peek.2023-07-07.14-42.mp4

[ryantxu]

works for me :)