Allow Scripted fields to be used in TSVB (Visual Builder)

[rahulsinghai]

Kibana version: 5.5.2, 6.2.2

Elasticsearch version: 5.5.2, 6.2.2

Server OS version: Linux 64 bit

Browser version: Google Chrome 63.0.3239.108 (Official Build) (64-bit)

Browser OS version:

Original install method (e.g. download page, yum, from source, etc.):

Description of the problem including expected versus actual behavior:

Steps to reproduce:

1. Create a scripted field: Language: painless Script: 0
2. Create a new visualization of Visual builder type
3. The new field is not available for Sum (or any other) aggregation
4. Create a new visualization of Metric type
5. The field is available for aggregation

Errors in browser console (if relevant): None

Provide logs and/or server output (if relevant): None

Describe the feature:
A scripted field should be available for creating aggregations in "Visual Builder" type visualization.

[timroes]

This is currently blocked by #15875

[timroes]

Duplicate of #13928

[ghost]

+1