Move VSCode context strings into constants file.

[sagerb]

Intent

Resolves #1864

Type of Change

• • [ ] Bug Fix
• • [ ] New Feature
• • [ ] Breaking Change
• • [ ] Documentation
• • [x] Refactor
• • [ ] Tooling

Approach

I searched for any string occurrence of "posit.publisher." and moved context related definitions into constants file.

Automated Tests

Directions for Reviewers

Verify functionality impacted:

[ ] Storage location for last selected deployment and configuration file [ ] Availability of these command pallette commands once the Home View has initialized:

• Select Deployment
• New Deployment
• Go to Debug Log
• Go to Publishing Log
• Browse Deployment Server
• Show Content Logs [ ] Context menu items or right-clicks
• View Deployment in Connect for successful deployments (content records), but not for pre-deployment or deployment errors
• Delete option (right-click menu) for credentials