[api] annotate public API with `@since` jsdoc comment

[pichlermarc]

Description

It's currently hard for instrumentation authors to define a minimum API version to depend on. Finding when a feature was added requires looking through the diff and cross-referencing the commits and associated PRs with releases across two repositories (https://github.com/open-telemetry/opentelemetry-js/releases and the now archived https://github.com/open-telemetry/opentelemetry-js-api/releases repo).

Therefore we should annotate all parts of the public API with a @since jsdoc that notes the API version that they were introduced in.

For this issue to be considered done we need to:

• add @since to the jsdoc of each exported public type
• add @since to each methods and properties when they were added after the enclosing type's @since annotation