v0.11.0

Stable-channel republication of 1.1.0-beta.15. Depends on dartastic_opentelemetry_api: ^0.11.0.

The minor bump from 0.10.0 carries four breaking changes:

• enabled becomes isEnabled() on tracers, loggers, meters and instruments, following the API. Replace
  x.enabled with x.isEnabled(). The enabled getters on the three providers are unchanged.
• OTEL_RESOURCE_ATTRIBUTES values are always strings
  (#206), no longer coerced to int or
  bool where they looked numeric, which changed their type on the wire.
• OTEL_RESOURCE_ATTRIBUTES values are percent-decoded, so k=a%2Cb now yields a,b.
• Exemplar.fromMeasurement takes a Measurement again rather than its spread fields.

Also notable: exemplars are sampled through an ExemplarFilter and ExemplarReservoir per the metrics spec
(#154), attribute limit environment variables
are parsed (#73), the secure parameter is
honored for logs and metrics (#253), and
OTEL_RESOURCE_ATTRIBUTES is read even when detectPlatformResources is false.