Expose unwrap on Helidon metrics API builder types

[tjquinno]

Environment Details

• Helidon Version: 4.x
• Helidon SE or Helidon MP
• JDK version:
• OS:
• Docker version (if applicable):

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Problem Description

The Helidon neutral metrics API exposes an abstraction of metrics behavior, similar to but not identical to Micrometer's approach.

We did not intend to include every feature of Micrometer in the Helidon API but by implementingunwrap allow developers relatively easy access to Micrometer features (or features of other potential implementations) not included in our neutral API.

The main level types (for example Counter and Timer) have unwrap but the builder types do not and it would be helpful if they did.