fix: Expose base, "underlying" table for Partitioned Table Enhancements

[AkshatJawne]

Closes deephaven/web-client-ui#2079 (All the core changes, web-client-ui changes to come in corresponding PR)

Changes Implemented

• Create a baseTable member variable and have a corresponding getter method, in order to be able to expose it for Partitioned Tables, as desired in point 1 of this epic

[AkshatJawne]

Applying spotlessApply to resolve Quick CI fix, then repushing -- taking long to start Gradle Daemon

[AkshatJawne]

Ready for re-review

[mofojed]

Discussing with @niloc132 a bit, there's a couple of changes we want to make.

• Main change - we want to deprecate the getKeyTable method, and instead the UI should be able to get the keys from the baseTable
  • Limit viewport to the key columns that matter when setting the viewport
  • Means we don't create and subscribe to two tables unnecessarily, better performance
  • To deprecate the method, we still need it to work - but instead of assigning keys table in the refetch method, we want to lazily fetch it when the getKeyTable() method is called. Then UI has a bit of grace period before it needs to update

[AkshatJawne]

Will make changes here (getKeyTable deprecation), changes to have view on keys table in : #5669

[AkshatJawne]

Looking into failures here