Add DebuggerDisplay to Activity and friends

[JamesNK]

Activity doesn't have a great debug experience:

Add DebuggerDisplay and DebuggerTypeProxy to make it easier to discover important information. For example, OperationName in the debugger display. And make it easier to view baggage and tags set on an activity.

Tagging subscribers to this area: @thaystg
See info in area-owners.md if you want to be subscribed.

Issue Details

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Activity doesn't have a great debug experience:

Add DebuggerDisplay and DebuggerTypeProxy to make it easier to discover important information.

Author:	JamesNK
Assignees:	-
Labels:	area-Debugger-mono
Milestone:	-

Tagging subscribers to this area: @dotnet/area-system-diagnostics-activity
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Activity doesn't have a great debug experience:

Add DebuggerDisplay and DebuggerTypeProxy to make it easier to discover important information.

Author:	JamesNK
Assignees:	-
Labels:	untriaged, area-Debugger-mono, area-System.Diagnostics.Activity
Milestone:	-

[ericstj]

@tarekgh is this something we're planning for 9.0?

[JamesNK]

I suggest adding the help wanted tag if the diagonstics team doesn't have time to look at this.