feat(cwl): Emit telemetry when starting and stopping liveTail sessions

[keeganirby]

Problem

Cloudwatch wants to monitor usage metrics of the LiveTail integration

Solution

When starting a session emit telemetry for:

• Session already started (this case happens when session is already running, and customer sends a new command that matches the already running session)
• Has LogEventFilter
• LogStream filter type
• Source of the command (command palette, explorer)

When closing a session:

• Session duration
• source of cancellation (ex: CodeLens, ClosingEditors)

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License: I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-actions]

• This pull request implements a feat or fix, so it must include a changelog entry (unless the fix is for an unreleased feature). Review the changelog guidelines.
  • Note: beta or "experiment" features that have active users should announce fixes in the changelog.
  • If this is not a feature or fix, use an appropriate type from the title guidelines. For example, telemetry-only changes should use the telemetry type.

[jpinkney-aws]

i'm still not sure why we can't just upstream these to commons

[keeganirby]

I was just following the documentation here: https://github.com/aws/aws-toolkit-vscode/blob/master/docs/telemetry.md. I did this in VSCode so my local builds would generate the telemetry objects and I could bundle adding the metrics as well as using them in the same PR. If I need to update commons instead I can send a change for that.

[keeganirby]

Opened PR to upstream to Commons. aws/aws-toolkit-common#916

[jpinkney-aws]

instead of prefixing these with the product name like we have in the past, you can probably drop the product name as the prefix so that we can make these more general