[ML] Edit swim lane on a dashboard opens two flyouts

[Dosant]

Kibana version: 7.8+, master
Describe the bug:

There's an EuiFlyout inception that is happening when opening the "JobSelectorFlyout" flyout from Dashboard.

Steps to reproduce:

1. Open a dashboard with swim lane
2. Edit swim lane
3. Watch as you see two levels of flyouts appear during the animation. Once they're fully open it's hard to tell until you search the rendered dom.

Expected behavior:

One flyout. The two flyouts can cause the animation to be sluggish and stutter. It will also cause problems with the EUI upgrade that pushes the panel below the header. Nested flyouts will double that amount.

Any additional context:

1. Same as [Dashboard] Add panel flyout opens 2 flyouts #64789
2. Example fix: [bugfix] Add panel flyout opens 2 flyouts #65861
3. Issue is caused by using core.overlays.openFlyout(<EuiFlyout></EuiFlyout>). <EuiFlyout/> - shouldn't be used in this case, as core adds own one.

[elasticmachine]

Pinging @elastic/ml-ui (:ml)