Add Cadence 1.0 Mode

[jribbink]

Issue To Be Solved

With changes to how Cadence 1.0 installations are managed coming to the Flow CLI (& a standardized command name) onflow/flow-cli#1410, it is only intuitive that we add support in VSCode to easily switch to this setting.

Currently, using Cadence 1.0 in VSCode means either replacing your pre-C1.0 CLI or specifying a custom cadence.flowCommand

This can now be achieved by adding a Cadence 1.0 mode which defaults to flow-c1 instead of flow command inside of VSCode.

(Optional): Suggest A Solution

• Add a setting in VSCode to switch to C1.0.
• Update messaging about how to use C1.0 in CLI.
• Potentially add UI piece that helps with this (i.e. at bottom of VSCode window)