4.x SE meters should have default scope of application instead of no scope

[tjquinno]

Environment Details

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

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Problem Description

In the new Helidon metrics API, each meter can have a different scope (formerly called "registry type" in 3.x) or no scope. Currently, if the developer creates a meter without setting the scope explicitly or without setting the default scope in the MetricsConfig then the meter has no scope.

This is different from 3.x (in which the default scope was always application.)

For ease of migration, the new metrics API in SE should use application as the default scope (unless the developer changes it using MetricsConfig).