Restructure to include metrics and merge specs together - prototype 1

[Emily-Jiang]

This PR demonstrates the following structure:
spec
tck

• tracing
• metrics

The advantages:

• fully embrace the common parts and separate for spec point of view
• clear separation of spec and tck
• TCK shares the same build infrastructure

Disadvantage:

• The existing tracing tck jar has to use a different group id.

[Azquelt]

The current project layout looks like this: (formatted as folder-name:maven-coordinates)

• root: org.eclipse.microprofile.telemetry:microprofile-telemetry-parent
  • tracing: org.eclipse.microprofile.telemetry.tracing:microprofile-telemetry-tracing-parent
    • spec: org.eclipse.microprofile.telemetry.tracing:microprofile-telemetry-tracing-spec
    • tck: org.eclipse.microprofile.telemetry.tracing:microprofile-telemetry-tracing-tck

With this proposal, the project layout would look like this:

• root: org.eclipse.microprofile.telemetry:microprofile-telemetry-parent
  • spec: org.eclipse.microprofile.telemetry:microprofile-telemetry-spec
  • tck: org.eclipse.microprofile.telemetry:microprofile-telemetry-tck-parent
    • metrics: org.eclipse.microprofile.telemetry:microprofile-telemetry-metrics-tck
    • tracing: org.eclipse.microprofile.telemetry:microprofile-telemetry-tracing-tck

Note that now all the artifacts are under the org.eclipse.microprofile.telemetry groupID.

The spec source files are arranged like this:

• spec
  • src/main/asciidoc
    • microprofile-telemetry-spec.asciidoc
    • metrics.adoc
    • tracing.adoc

[Azquelt]

Looks good 👍