Add upgrade installer

[jstvz]

This PR adds a hidden upgrade-only installer.

Critical Changes

Changes

Issues Closed

New Metadata

Deleted Metadata

Definition of Done

Refer to Definition of Done to see any additional details for the items below:

• Any net new LWC work has JEST test coverage 50% or above
• Default Sa11y tests pass for all LWC components
• 🔒 Secure both Front-end (LWC) & back-end (Apex) as necessary
• 🔑 Grant users access in Permission Sets (Object, Field, Apex Class) as necessary
• Link the pull request and work item by PR comment and Chatter post respectively, e.g. GUS: W-0000000: Work Name
• Make sure that ACs are updated (if any gaps)
• All acceptance criteria have been met
  • Developer
  • Code Reviewer
• Pull Request contains draft release notes
• Labels, help text, and customer facing messages are reviewed by Docs
• QE story level testing completed