Unified logging setup for Swift extension

[award999]

Description

• Add winston dependency that will log to a file always, and to the Swift output channel at the level specified by the new swift.outputChannelLevel setting
• Deprecate the swift.diagnostics setting but check it to set the output channel to debug if the swift.outputChannelLevel setting is not explicitly set
• No longer use RollingLog to hold log messages in memory unless running the extension under tests
• Modify SwiftOutputChannel used by the LSP to extend this new login functionality, but allow it to be treated like an output channel

Issue: #1755

Tasks

• Required tests have been written
• Documentation has been updated
• Added an entry to CHANGELOG.md if applicable

[rbenegal]

Looks good to me thanks! Just some minor typo suggestions.

[matthewbastien]

Looks great! This will help a lot with our logging.

Just one minor comment about the name of the setting.