Should alert action params form clear values when changing "Run when"?

[mikecote]

I was testing this PR (#83226) which now sets defaults based on action type and action group (really great!). Since some default values are set each time the "run when" changes, the defaults get blended with existing values by overwriting them.

I'm opening this issue to discuss what behaviour we should have? Keep everything as is? Clear all form values and apply defaults each time the "run when" changes? Clear some form values and apply defaults each time?

Scenario with #83226:

1. Create a PagerDuty connector
2. Fill out a create alert form
3. Add PagerDuty connector
4. Set PagerDuty summary to "Alert condition is met!"
5. Change "Run when" to "Resolved"

You'll notice the form is in a state like below where "event action" is now "Resolve" but the old summary is now irrelevant.

Screenshot

Note from @ymao1

I feel like the expected behavior might be different per connector or even connector field. If I filled out my email address but forgot to change the "Run when", it would be annoying to have that cleared

cc @mdefazio

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)