Track block building strategy as a metric

[wemeetagain]

Our 1.11.0 release had a bug that prevented us from building blocks via the builder.
Unfortunately this wasn't caught in beta testing because we have no visibility in our metrics into what strategy being selected and why.

We should track when we select builder vs local block building and why.

[philknows]

I think this is important to try and implement sooner rather than later... it would also provide us with good metrics relating to our prod nodes and how the min-bid set affects the various strategies when using mev-boost. Can someone work on this for v1.13?

[nflaig]

• Should be implemented together with mev-boost metrics #6108. I can work on those

[nflaig]

Not resolved yet