Async commit hook and OSGi

[Davide Giannella <da...@apache.org>]

hello team,

as part of OAK-2472 I'm introducing the concept of asynchronous commit
hook. Read it as asynchronous processing of EditorProvider.

The code is still in early stages and will require clean-up and proper
refactoring later on.

To achieve the concept of asynchronous EditorProvider I added an
interface:AsyncEditorProvider

https://github.com/davidegiannella/jackrabbit-oak/blob/OAK-2472/oak-core/src/main/java/org/apache/jackrabbit/oak/spi/commit/AsyncEditorProvider.java

it doesn't do anything in particular other than adding a "semantic
flavouring" to the EditorProvider.

While it's registered easily using the .with() I saw some providers
declare the @Component and @Service (NamespaceEditorProvider) and some
don't (IndexUpdateProvider).

So I'm wondering if/where I should put any OSGi thing to instruct the
framework about the asynchronous aspect of the editor. If not, why do we
declare the @Component and @Service on the editor providers?

Thank you
Regards
Davide