fix: [Obs Infrastructure > Hosts][KEYBOARD]: Logs tab at the bottom o…

…f the page cannot be scrolled by keyboard (elastic#184003)

Closes: https://github.com/elastic/observability-dev/issues/3421
Closes: https://github.com/elastic/observability-dev/issues/3407
Closes: https://github.com/elastic/observability-dev/issues/3412
Closes: https://github.com/elastic/observability-dev/issues/3418
Closes: https://github.com/elastic/observability-dev/issues/3421
Closes: https://github.com/elastic/observability-dev/issues/3424

## Summary

The Obs Applications > Host Detail page has aLogs table that includes a
hover-only detail view. This needs to also be keyboard focusable to be
available to all users. Screenshot attached below.

## Steps to recreate
1. Open the [Obs
Hosts](https://issue-serverless-bdwqw-pr183659-f2d99b.kb.eu-west-aws.qa.elastic.cloud/app/metrics/hosts)
view
2. Click on one of the host name links
3. When the Host Detail opens, click on the Logs tab
4. Use the Tab key to move through the table
5. Verify the table row [ ... ] never appears when navigating by
keyboard

## What was changed?: 

All the above-mentioned errors use a single component`
x-pack/plugins/observability_solution/logs_shared/public/components/logging/log_text_stream`
and can be fixed within it.

1. tab-index has been added to vertical_scroll_panel.tsx.
2. The logic displaying the button with menu has been updated using CSS.

x-pack/plugins/observability_solution/logs_shared/public/components/logging/log_text_stream/scrollable_log_text_stream_view.tsx

@@ -204,7 +204,7 @@ export class ScrollableLogTextStreamView extends React.PureComponent<
                         onVisibleChildrenChange={this.handleVisibleChildrenChange}
                         target={targetId}
                         hideScrollbar={hideScrollbar}
-                        data-test-subj={'logStream'}
+                        data-test-subj="logStream"
                         isLocked={isScrollLocked}
                         entriesCount={items.length}
                       >

x-pack/plugins/observability_solution/logs_shared/public/components/logging/log_text_stream/vertical_scroll_panel.tsx

@@ -248,6 +248,8 @@ export class VerticalScrollPanel<Child> extends React.PureComponent<
         scrollbarOffset={scrollbarOffset}
         onScroll={this.handleScroll}
         ref={this.scrollRef}
+        tabIndex={0}
+        className="eui-scrollBar"
       >
         {typeof children === 'function' ? children(this.registerChild) : null}
       </ScrollPanelWrapper>