Add missing @since tags across the code base where appropriate

[sbrannen]

Overview

I unfortunately don't have time to determine all locations where @since tags are missing within the code base, but I have noticed that features have recently been added without @since tags.

For example, the new getObservationRegistry() and setObservationRegistry(...) methods were added in 1.10.8, but the class-level Javadoc for ObservationThreadLocalAccessor makes it appear that these methods have existed since 1.10.0, which is not true.

Related Issues

• Introduce TestExecutionListener for Micrometer's ObservationRegistry in the TestContext framework spring-projects/spring-framework#30658

[sbrannen]

At a glance, it appears that several constructors and methods in ObservationThreadLocalAccessor were introduced in 1.10.8 without @since tags.

[marcingrzejszczak]

Yup, will fix that ASAP