Fix ESM build path

[jackw]

This PR fixes the mentioned issue regarding mismatched "module" path and esm dist path.

It also:

• cleans up the circular dependencies that esbuild warns about
• fixes broken prettier config looking for @grafana/toolkit. See old config on unpkg.
• replaces export * with named exports to make it explicit what is part of the public api.
• fixes weird imports of entire packages like react, @grafana/ui, @grafana/data and @grafana/experimental in ESM builds due to the unused export { NewConnectionConfig } from './NewConnectionConfig';in components/index.ts.
• prevents ESM builds including a copy of @emotion/css in dist/esm/node_modules/@emotion

Fixes: #73

Notes for reviewers:

I have not tested this against any plugin builds nor have I tested it against a build of Grafana core yet.

[sarahzinger]

hmmm. just a heads up that I just realized I get errors like this in the console when I use this with athena... but I confirmed I see the same thing when I install the main version of this sdk, so I believe unrelated to this pr. Just sharing in case it comes up for others while reviewing. Would be something good to sort out before we publish a new version though (although wouldn't be surprised if the fix is in athena and not in this package).