More OpenTelemetry changes

[majocha]

• Add activity wrapping a test run to easily distinguish traces generated from testhost. Group by assembly + net framework.
• log point-in-time events as events with data instead of activities to declutter traces. (for example StackGuard.Guard)
• Enable trace provider in vsix when build in debug configuration: For example build VisualFSharpDebug in debug mode and start an instance with "Start WIthout Debugging" will produce traces viewable in Jeager.

[github-actions]

❗ Release notes required

@majocha,

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Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/9.0.300.md	No release notes found or release notes format is not correct
vsintegration/src	docs/release-notes/.VisualStudio/17.14.md	No release notes found or release notes format is not correct