Webview cleanup

[Benjin]

I noticed some inconsistencies in how we were building webviews, and brought everything into alignment:

• contexts are all named context, states are all named state; before, we were mixing the names which led to some confusing code snippets where a variable named state was not actually the state.
• contextProp interfaces and providerProp interfaces are now consistently named across all webviews; similarly, we were calling some things that weren't state "state"
• removing unnecessary null propagation and non-null-assertion operators; instead, we should be checking that context is defined and returning if not.
  • We should only use myVar!.something if the type checker is unable to figure out that it's not null/undefined on its own. Usually, we should add checks to help the type checker along. Using a non-null assertion operator is a yellow flag that something may be wrong.
• Promoted instances where we had an explicit provider property in the context so that all the RPC functions for the webview are accessible directly.
  • This one isn't fixing an issue, just bringing things into alignment. I could've also done the opposite, and "demoted" the RPC definitions where they were directly under the context object. Happy to go either way, but we should keep consistent to make future work and debugging simpler. Any opinions?

[github-actions]

PR Changes

Category	Main Branch	PR Branch	Difference
Code Coverage	50.45%	50.60%	$${\color{lightgreen} .15\% }$$
VSIX Size	12144 KB	12142 KB	$${\color{lightgreen} -2 KB \space (0\%) }$$
Webview Bundle Size	3176 KB	3176 KB	$${\color{lightgreen} 0 KB \space (0\%) }$$

[aasimkhan30]

Looks good to me. Thanks for cleaning the code!