[Spike] Investigate the feasibility of CSS anchor positioning

[weronikaolejniczak]

The purpose of this issue is to investigate whether we can use the new anchor positioning for EuiToolTip.

Let's consider our browserslist and make sure we test all browser versions we say we support.

Acceptance criteria

• Both of these are valid conclusions:
  • we can and will use this API for EuiToolTip
  • we cannot use this API for EuiToolTip yet, in which case a summary is made on the below-linked ticket

See #7102 for more info.