Add events to span detail pane

[JamesNK]

Fixes #1463

• Adds events to the span detail pane.
• Adds extra content template to support displaying span event attributes when present
• Updates span detail pane to use an accordion.
  • By default, high-level span details are open and application and span events are closed.
  • The accordion allows the pane to support more information. An alternative approach would be a tab control, but an accordion allows sections to be viewed side by side and feels more appropriate right now.
  • This UI or something similar will be needed in a resources detail pane in the future (i.e. a section for high-level resource information, a section for endpoints, a section for environment variables, etc)
• Event count is visible in accordion if there are one or more events (so people know whether it is worth expanding event section).

Microsoft Reviewers: Open in CodeFlow

[JamesNK]

cc @rolfik-mycronic @davidfowl

[tlmii]

Do you have a screenshot of what this looks like? I'm having trouble envisioning a property grid within a property grid value column given our information density already.

[JamesNK]

Span events are rare. I've never seen events with attributes in the real world (I had to add some fake data to get the UI to show up). I don't expect this UI to be shown much at all.

I think it is Good Enough until there is feedback otherwise.

[JamesNK]

Added a header to make it clearer what the values are:

[tlmii]

👀 that's weird.

[JamesNK]

🤷