(Accessibility) Multiple apps missing <h1> tag or content for <h1> tag or have nesting defects

[barlowm]

Dashboard page
The initial panel with the dashboard name (sample data sets) is an H3, where others are H2s, creating a nesting mis-match. Screenshot at the bottom of the description.

Discover page

<discover-app class="app-container">
<h1 class="euiScreenReaderOnly"></h1>

• Dashboard
• Discover
• Canvas page - No <h1> Tag at all
• Machine Learning page - No <h1> Tag at all
• Metrics page - No <h1> Tag at all
• Logs page - No <h1> Tag at all
• APM page - HAS <h1> Tag but heading nesting is not maintained (<h1> followed by an <h3>)
• Uptime page - HAS <h1> Tag but heading nesting is not maintained (<h1> followed by an <h3>)
• SIEM page - No <h1> Tag at all
• Dev Tools - HAS <h1> Tag but heading nesting is not maintained (<h1> followed by an <h2> followed by an <h4>)

Kibana Version:
7.6.2

OS:
Windows 7

Browser:
Chrome

Screen reader: [if relevant]
N/A

Relevant WCAG Criteria: [#.#.# WCAG Criterion - Level A/AA/AAA](link to https://www.w3.org/WAI/WCAG21/quickref/)
2.4.6 - Headings and Labels - Level AA
Headings and labels describe topic or purpose.

Screenshots

[1Copenut]

This seems correlated with #42379. I'm in favor of setting focus on the H1 of a page view when we swap URLs using client-side routing, so screen readers announce the change properly. I'll do some more research, but I think these are related items.

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)

[Heenawter]

I have removed the @elastic/kibana-presentation tag, because we have completed both the Canvas and Dashboard requests 👍

[jughosta]

Discover page: fixed in #129789

[elasticmachine]

Pinging @elastic/siem (Team:SIEM)

[elasticmachine]

Pinging @elastic/unified-observability (Team:Observability)

[elasticmachine]

Pinging @elastic/uptime (Team:uptime)

[justinkambic]

PR for Uptime here: #136559

EDIT: Uptime fix merged.

[1Copenut]

Machine Learning section has appropriate H1 tags in 8.5 main branch pulled to local machine on 12 September.