Fix buttons must have discernible text issue by adding aria-label

[maryam-saeidi]

Fixes #179490

Summary

This PR fixes buttons must have discernible text issues by adding aria-label to the EuiButtonEmpty components.

[elasticmachine]

Pinging @elastic/obs-ux-management-team (Team:obs-ux-management)

[apmmachine]

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Just comment with:

• /oblt-deploy : Deploy a Kibana instance using the Observability test environments.
• /oblt-deploy-serverless : Deploy a serverless Kibana instance using the Observability test environments.
• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: f148341

Failed CI Steps

• Jest Tests #12

Test Failures

• [job] [logs] Jest Tests #12 / unified data table should update row Height correctly
• [job] [logs] Jest Tests #12 / unified timeline unified field list should remove the column when clicked on X sign

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
observability	263.5KB	263.6KB	+66.0B

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@elasticmachine merge upstream

cc @maryam-saeidi