fix(cwl): Hide LiveTail CodeLenses and display info message when closing session

[keeganirby]

Problem

Currently after closing a session in a way that leaves the TextDocument open (Stop tailing CodeLens), the codeLenses remain visible. This means a user could click Stop tailing again, and receive an error for not being able to find the running LiveTail session for the given document.

Additionally, there is no feedback when a session is closed. Clicking Stop tailing doesn't signal to the user that the session was actually stopped.

Solution

• Provide a refresh method in the LiveTail CodeLens provider. This fires an event to force recomputing the CodeLenses on a document.
• Modify LiveTail Lens provider to return no Lenses if the session is not running (in the registry)
• Display an information window when a Session is stopped
• Changes wording/placement on some log statements for consistency.

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

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