Remove old "Explore underlying data" action

[drewdaemon]

In #127355 we added a Lens-specific successor to the old “Explore underlying data” action. That original action (issue) ended up not working well and, hence, being turned off by default (as of #70045).

The original action still exists in our code base and FTR suite. Users have to explicitly enable this old action via an undocumented property in kibana.yml and when I last checked the telemetry (a year ago) usage was close to nonexistent.

Let's remove it!

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[jughosta]

Linking to #155852

[kertal]

in our grooming session we discussed and rather than removing it we also might consider to improve it. Anyway, I think this needs alignment and discussion from product side, so assigning to @ninoslavmiskovic and we will discuss it, how to move forward

[drewdaemon]

@kertal makes sense. I will say that, at the time at least, we saw this as the successor to the action described in this issue. But, even the successor is recently under UX scrutiny.