Add metric view YAML serde package - #6837

Changes

• Add libs/metricviews with typed YAML parsing and serialization for versions 0.1, 1.0, and 1.1, including single-source and multi-source views.
• Normalize backend-equivalent values for drift comparisons, and cover the supported shapes with 47 generic fixtures.
• Preserve quoted parameter defaults and YAML aliases; reject unsupported v1.1 view types and multi-source shapes without their discriminator.

Why

Provide reusable Go parsing and serialization for Databricks metric view YAML, independent of bundle resource wiring.

Tests

• go test ./libs/metricviews -count=1
• Full repository checks were skipped as requested.

PR description drafted with Codex.