TSVB: Different field format on different series is ignored

[tiagoveigalazaro]

Kibana version: 7.8.1

Elasticsearch version: 7.8.1

Describe the bug:

When creating a TSVB visualization with two different series each with their field formatting, then the first format is used for both.

This is both visible on the

P.S.: would be pretty nifty if we could specify the Axis format independently of the series.

Steps to reproduce:

1. Create a TSVB visualization
2. Create a first series and customize its format
3. Create a second series and customize its format with something different
4. Switch the order and see that the format changes to the first one

Expected behavior:

I'm not sure this is a "feature not a bug" kind of situation, but in many cases we're comparing different metrics in the same context (in the example below CPU usage vs CPU Requests in a Kubernetes cluster) and without the format to separate both gets pretty hard to distinguish.

Screenshots:

[elasticmachine]

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