Remove "name" field from Metric Definition schema

What does this MR do and why?

This is one of several MRs to remove name from metric definitions. See: #411602 (closed)

This MR removes name from the metric definition schema. As of #411602 (closed) we no longer add name to new metric definitions and with !128353 (merged) name will be removed from all existing metric definitions.

MR acceptance checklist

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Related to #411602 (closed)