[discover] implement k7Breadcrumbs

[spalger]

Fixes #25894

Summary

This PR updates the discover routes to provide k7Breadcrumbs used by the new header navigation. See #25884 for general information about the integration with the router and #25689 for the breadcrumb taxonomy

Checklist

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support

[elasticmachine]

Pinging @elastic/kibana-app

[cchaos]

A couple questions:

1. What is the relationship between the breadcrumb title, local title, and tab name here? Seems it can be simplified?
   

2. Shouldn't the single doc viewer also have the "Discover" breadcrumb?
   

[spalger]

@cchaos re 1, I'm not sure. I tried putting the id, or the index, in the breadcrumb, but they both just got tucked into ellipses and then I kind of figured that "Context" kind of described this page better than "Surrounding ...".

re 2, yeah, it probably should.

[cchaos]

1. I think we can fix the truncation issue in EUI by not truncating the last item unless it touches the right side controls. I think it'll be nice to put that title up in the breadcrumbs. But I can't figure out what is the right one to put up there.

2. We should probably move the doc id in the doc viewer page to the breadcrumbs and get rid of the tabs as there can never be more than one...(?)

[cchaos]

Maybe the breadcrumbs should be:

Discover / Context of _doc#p7SkdWcBMSKbnGD8wwQB

for context, and

Discover / _doc#p7SkdWcBMSKbnGD8wwQB

for single doc viewer, and get rid of that extra title and "Surrounding Documents..." and the tabs.

But then do we think it's important to show the index pattern name somewhere?

[spalger]

I think the index pattern is more important than the type (_doc) since types are deprecated/removed in 7.0 anyway.

Avoiding truncation of the last breadcrumb based on available space would ease my worries, so let's go for that!

[spalger]

[elasticmachine]

💔 Build Failed

• continuous-integration/kibana-ci/pull-request

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request

[cchaos]

I think that makes sense to me!