[APM] Replace ui/kfetch with core.http

[dgieselaar]

Closes #46548.

This replaces the static import ui/kfetch with the injected http module from core. To accommodate this, several changes were made:

• Change callApi's signature from ( options ) to ( http, options ).
• Expose a useCallApi hook that uses useKibanaCore to get http from context.
• Change callApmApi to a factory function that needs http. I could not get a similar (http, options) signature to work because I could not extract the type of options from callApmApi, presumably because it is a generic.
• Expose a useCallApmApi hook, similar to useCallApi.
• Inject callApmApi as the first argument to the callback passed to useFetcher. I figured this is a little better than using a separate hook because it a) removes the need for an extra import/hook b) avoids the dependency dance for useFetcher.
• use useFetcher in useApmIndexPattern

[elasticmachine]

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[rudolf]

Small nit on the docs for HttpFetchError but otherwise Platform changes LGTM

[rudolf]

Can you add an block comment above the definition of HttpFetchError like:

/*
 * @public 
 */

That will make this warning go away and mark the type as part of the public API

[dgieselaar]

Fixed. That comment format specifically seemingly did not work, but /** @public */ did.

[elasticmachine]

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[sorenlouv]

why never?

[dgieselaar]

For some reason TS expects never as a type. I'm probably doing something wrong, but I couldn't figure it out and didn't want to spend too much time fixing types for a test. Do you happen to know what's going on?

[sorenlouv]

What do you think about:

    function getCoreMock(res: HttpBody) {
      return ({
        http: {
          basePath: {
            prepend: (path: string) => `/basepath${path}`
          },
          get: jest.fn(res)
        },
        notifications: {
          toasts: {
            addWarning: () => {}
          }
        }
      } as unknown) as LegacyCoreStart & {
        http: { get: jest.SpyInstance<LegacyCoreStart['http']['get'], any> };
      };
    }

This way the spies are not modified, and the compile error disappears

[dgieselaar]

I think my type was just wrong. Simplified to { get: jest.Mock<any,any> } and that works as well.

[sorenlouv]

👍

[dgieselaar]

@sqren I've merged in your changes and did some rudimentary checks that the agent configuration things that you merged in still working, but can you do some surface checks as well just to be sure?

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[sorenlouv]

lgtm. Did some manual testing of agent configs and still works as expected 👍