[Story] UI for creating Event Templates

[andrewazores]

Currently, to create a new Custom Event Template, users need to upload an XML document from their local machine to the Cryostat backend. They either start from scratch or, more commonly, download an existing (Continuous or Profiling) template from Cryostat, then edit this with a plaintext editor.

We should have a UI that allows users to define a Template within -web using some form/wizard so that this can be accomplished graphically, without editing XML by hand or having to import/export from JMC's template editor. The existing information about event types can be reused here to provide hinting for events and options that can be defined in the XML, however it's important to also allow manually-defined values here since there may be application-specific unregistered event types that will show up in the recording.

The user should also be able to define these templates as extensions/overrides from other existing templates, either Custom or Target templates.

[andrewazores]

The jfr cli tool has a new configure option that does a basic version of what we want here too. Worth looking into, at least for inspiration.

https://egahlin.github.io/2022/05/31/improved-ergonomics.html