[Request] UI for starting "a recording" using multiple event templates

[andrewazores]

Describe the feature

JFR does not actually support the notion of a single recording which uses multiple event templates, but it would be a nice UX.

1. Cryostat can merge the event template models for all of the templates the user has selected, creating a "synthetic template", and apply that to the recording.
2. Cryostat, or the UI, can handle a request for an N-multi-template recording as actually a request for N recordings - one for each template. Other recording properties (metadata labels, maxage/maxsize/todisk) can be mirrored across them all. This approach may lead to some confusion about the recordings all appearing separately, despite the fact that the JFR data stream from each should be equivalent.

This would allow the user to pick and choose from various layered templates, ex. "Continuous + Quarkus + Hibernate", without needing to manually create three recordings. This would also help surface the fact that recordings can be layered and combined in this way.

Related to #225.

Anything other information?

No response