Feature/graphql metrics

[MikeKry]

Add graphql metrics support as suggested in #4257.

• added conditional enabling of metrics from settings
• added header activated metrics as in https://graphql-dotnet.github.io/docs/getting-started/metrics/
• added apollo tracing & InstrumentFieldsMiddleware activation
• added possibility to add custom field middleware to graphql schema by registering implementation of ICustomfieldmiddleware

[github-actions[bot]]

This pull request has merge conflicts. Please resolve those before requesting a review.

[Piedone]

I sincerely apologize for us taking so much time here. I checked out the PR, going over old ones, and this would be quite useful.

Is this something you'd like to revisit any time soon @MikeKry or should we close? If you fix the build error and merge conflict, I'll review ASAP.

[Piedone]

@MikeKry what do you think?