feat(cwl): Add metric definitions for LiveTail

[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.

[jpinkney-aws]

cc @dhruvigajjar