feat: use shared GBOS core model

[cdsap]

InfoKotlinProcess now uses the published GBOS core model for its opt-in Develocity observations while preserving the existing output shape and defaults.

What changed

• Adds io.github.cdsap:build-observability-core:0.0.6 as a runtime dependency.
• Builds typed producer, attribute, measurement, and observation values through the shared core model.
• Keeps build-observability-schema:0.0.4 and the schema validator test-only.
• Preserves GBOS opt-in behavior and legacy output when disabled.

Validation

• ./gradlew :infokotlinprocess:test
• Focused GBOS projection tests pass against core 0.0.6 resolved from Maven Central.