[Lens] Visualizations are tightly coupled to specific functions based on operation.dataType

[wylieconlon]

This is both cleaning up tech debt in Lens and setting us up for the date ranges and a combined number histogram/range function. The main issue is that we are coupling the data type and expected display behavior. The nice thing is that we already have a second parameter on OperationMetadata which should be used instead:

export interface OperationMetadata {
  dataType: DataType;
  scale?: 'ordinal' | 'interval' | 'ratio';

The main difference is that histograms are interval type, and other bucket aggregations are ordinal type. Here are the places that I have identified as needing to change:

• The XY suggestion logic looks at dataType === 'date' to determine the X axis. It should instead use operationMetadata.scaleType === 'interval', so that number histograms are placed on the X axis.
• Pie charts reject dataType === 'date' in suggestions, but instead they should reject scaleType === 'interval'
• The XY title logic uses special logic for dataType === 'date' when building titles. It probably should
• The handleFilterClick function on datatables is looking up the time field only for date histograms, but not date functions in general.

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)