migrate from @microsoft/microsoft-graph-client to @microsoft/msgraph-sdk-core

[baywet]

As part of the TypeScript SDK work, we're planning to deprecate the old JavaScript SDK.
Graph explorer should also follow that migration path.

Things to consider:

• bundle size after migration. We anticipate little to no impact, but reporting those numbers on the PR would be beneficial.
• middleware handlers: GE might want to tweak the handlers it's using to match the current setup. (e.g. do we want the retry handler or not, etc...)

Potential blockers:

• Kiota libraries only offer authentication providers for azure identity and spfx. GE uses msal. We might want to complete the support for MSAL ahead of this work
• kiota libraries are missing a raw request authorization middleware handler

Additional considerations:

• we might want to do that work AHEAD of the GA to benefit from the experience here and feed back in the GA cycle.

[musale]

Waiting on microsoft/kiota-typescript#186.