Update the VS Code timeout extend behaviour

[loujaybee]

We have updated timeout behaviours gp timeout set so that users can specify a range of timeouts, but VS Code only supports "extending" a timeout arbitrarily to three hours. This needs updating:

• Add the ability to specify a specific timeout value like gp timeout set
• Remove text that other workspaces have been updated

Relates to:

• Deprecate gp timeout extend and review timeout defaults #16083