Bug fixes for the ApiKeyProvider

[intentionally-left-nil]

When actually implementing the ApiKeyProvider, several type issues were discovered. This PR fixes:

• The api_key providers entrypoint is exported so it can be imported directly
• RuntError options are optional, and the empty {} can be omitted
• ListApiKeys takes in a limit/offset value
• ApiKeyProvider passes back an AuthenticatedContext, to prevent unecessary non-null assertions
• the index exports all the values from shared, not just the types