Upgrade jsdom to v15+

[1Copenut]

The EuiFieldNumber test file has a step assertion we can't run because of an older version of JSDOM. This work can be done after Jest has been upgraded in #6813.

[cee-chen]

Quick note: upgrading Jest to v25 (from current v24) will automatically get us to jsdom v15, so we don't necessarily have to go the whole way to latest Jest (which is now on v29)

[github-actions]

👋 Hi there - this issue hasn't had any activity in 6 months. If the EUI team has not explicitly expressed that this is something on our roadmap, it's unlikely that we'll pick this issue up. We would sincerely appreciate a PR/community contribution if this is something that matters to you! If not, and there is no further activity on this issue for another 6 months (i.e. it's stale for over a year), the issue will be auto-closed.