BUG #14559: Bring in VTK fixes for double-range support.

Also make pqTransferFunctionWidget render a narrower range of values
since we can now indeed support them.

Change-Id: I9e438d3f6b5bfa231bc89fa32a716e8b95c69f86
Merge topic '14599_fix_double_range_issues' into next

e76d2dba BUG #14559: Bring in VTK fixes for double-range support.
Update pqTransferFunctionWidget.

Change-Id: I1e030d45ecb64ade13a2a7c0e90aca4d99a79934
Merge topic '14599_fix_double_range_issues' into next

9dfe2e35 Update pqTransferFunctionWidget.