Use interface instead of type to allow for declaration merging

[shawnmcknight]

📝 Description

This PR modifies a few type aliases in the declaration file to instead be interfaces. As noted in #1164 , an interface can be augmented through declaration merging. This is important for consumers and third party plugins as it allows them to extend the built-in types. type will not allow this merging behavior.

This PR adjusts ActionSchema, EventSchema, ServiceEvent, and ContextParentSpan to all be interfaces instead of types. A few of these types also were intersections with ThisType<Service<S>>. In order to avoid breaking changes, the ServiceEvents type was adjusted to have the ThisType<Service<S>> instead so the type of this will be available in the appropriate contexts for service schemas. The ServiceActionsSchema type already included ThisType<Service<S>> so a change there was unnecessary.

A few additional unrelated changes were triggered due to prettier auto-formatting.

This PR supersedes and closes #1164 .

💎 Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

🚦 How Has This Been Tested?

I loaded the changed definition in a large repository of services and ran typescript type checking with no errors. Additionally, I augmented the ActionSchema type in a third party library successfully and was able to access the augmented types.

🏁 Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have commented my code, particularly in hard-to-understand areas

[icebob]

Awesome, thanks!