Time Series Visual Builder Bar Chart - Bars/columns are not centered

[ghost]

Kibana version: 6.5.0

Elasticsearch version:6.5.0

Server OS version:Windows Server 2016

Browser version: Firefox 64.0 (64-bits)

Browser OS version: Windows 7 Enterprise

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

Description of the problem including expected versus actual behavior:
Bars are drawn from the datapoint to the right instead of beeing centered around it. This is misleading to the user. For example if you hover over a bar the legend can show values from the bare to the right instead of the one the user is hovering over with the mouse. This means that I have to use line for the chart type because this confuses the end user.

See this post for a screenshot: https://discuss.elastic.co/t/time-series-visual-builder-bar-chart-bars-columns-not-centered/162951

Steps to reproduce:

1. Greate a time series visualisation with the Time series visual builder.
2. Select bar under Chart Type
3. The bars are drawn from the datapoint to the right instead of beeing centered around it.

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Describe the feature:
The bars are drawn centered around a time point.

[elasticmachine]

Pinging @elastic/kibana-app

[markov00]

fixed in #31417