[metrics builder] Add ability to enable/disable resource attributes

[dmitryax]

User should be able to enable and disable resource attributes the same way as it's currently done for metrics:

metadata.yaml interface changes for receiver authors

All resource attributes should get an additional field enabled. For now, let's keep all the existing attributes enabled by default, but receiver authors will be able to add (or turn existing) resource attributes into optional attributes. hostmetrics/processscraper example:

resource_attributes:
  process.pid:
    enabled: true
    description: Process identifier (PID).
    type: int

User config interface changes

This capability should generate additional struct for user configs that receiver authors have to include in their config the same way as done for MetricsSettings. Using the same example for process.pid resource attribute, the generated structs should look like this:

type ResourceAttributeSettings struct {
	Enabled bool `mapstructure:"enabled"`
}

type ResourceAttributesSettings struct {
	ProcessPid     ResourceAttributeSettings `mapstructure:"process.pid"`
}

[hughesjj]

for visibility: I hashed out most of the impl yesterday, currently debugging tests, and will probably reach out to Dmitrii for a second look @ the logic to exclude resource attrs in draft before publicizing.

[github-actions]

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[fatsheep9146]

This issue is resolved, right ? @dmitryax

[dmitryax]

Right, this PR will resolve it