Pass initialDisplay snapshot via separate param to showTrack

[cmdcolin]

The showTrack has a "initial snapshot" method that it can use to instantiate track specific state, but it is also useful to be able to initialize display specific state too (in the GDC plugin, we can use this to provide initial min and max scores for wiggle display for dynamically added tracks for example)

[codecov]

Codecov Report

Merging #1995 (cf86a35) into main (739a00e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1995   +/-   ##
=======================================
  Coverage   60.97%   60.97%           
=======================================
  Files         471      471           
  Lines       22512    22514    +2     
  Branches     5174     5230   +56     
=======================================
+ Hits        13726    13728    +2     
+ Misses       8510     8503    -7     
- Partials      276      283    +7     

Impacted Files	Coverage Δ
.../linear-genome-view/src/LinearGenomeView/index.tsx	83.81% <100.00%> (+0.05%)	⬆️
products/jbrowse-desktop/src/factoryReset.ts	0.00% <0.00%> (ø)
...s/alignments/src/PileupRenderer/PileupRenderer.tsx	56.67% <0.00%> (ø)
...y-jbrowse/src/JBrowse1Connection/jb1ConfigParse.ts	23.21% <0.00%> (ø)
...src/LinearPileupDisplay/components/FilterByTag.tsx	0.00% <0.00%> (ø)
...rc/LinearPileupDisplay/components/SetMaxHeight.tsx	0.00% <0.00%> (ø)
...eElementTypes/renderers/ServerSideRendererType.tsx	26.19% <0.00%> (ø)
...src/LinearBasicDisplay/components/SetMaxHeight.tsx	0.00% <0.00%> (ø)

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