fix: create jwt verifier once

[erinleigh90]

Description of changes

Creates the token JWT verifier during the createServerRunner process and stores in memory instead of on getItem. This allows us to maintain the JWKS in cache instead of calling the JWKS endpoint every time tokens are retrieved from localStorage.

Issue #, if available

#13706

Description of how you validated changes

Checklist

• PR description included
• yarn test passes
• Unit Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

Checklist for repo maintainers

• Verify E2E tests for existing workflows are working as expected or add E2E tests for newly added workflows
• New source file paths included in this PR have been added to CODEOWNERS, if appropriate

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.