Pom refactoring on OpenTelemetry related dependencies

[ppatierno]

This PR is similar to what is done on the bridge with strimzi/strimzi-kafka-bridge#891

• avoid using a otel version property as variable to declare otel alpha version. OpenTelemetry is moving to deliver different artifacts at difference pace, also some of them will be non alpha at some point. It's better having the explicit version then.
• because guava "jre" is already a direct dependency, it just add an explicit exclusion from the corresponding "androd" from otel and grpc dependencies (NOTE: it's already happening implicitly, but I think it's better having it explicitly for clarity).

[ppatierno]

/azp run regression

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