Single index shard legend spans way off to the right for nodes holding many shards

[inqueue]

Kibana version: 7.6.0

Elasticsearch version: 7.6.0

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

The index shard legend can run way off to the right for nodes holding many shards for a single index.

Steps to reproduce:

1. Produce an index with something like 60 shards.
2. Put all the shards on a single node.
3. Observe the index shard legend for the index.

Expected behavior:
Always show the shard legend in an easy to read scalable way.

Screenshots (if relevant):

Errors in browser console (if relevant):
no errors

Provide logs and/or server output (if relevant):
no logs

Any additional context:
The issue surfaced while performing a shard split on a 5TB index. Eventually shards will be distributed across other cluster nodes.

[chrisronline]

A little history here. There is an older PR that attempted to fix up various UI issues with the shard legend, but ultimately didn't get merged.

I think we need to reinvest some time into fixing issues with this and also potentially updating the UX around it.

[chrisronline]

Will address this from the meta: #65103