Split CLI commands from `log4j-1.2-api` and `log4j-core`

[ppkarwasz]

There are a couple of CLI commands in the current 2.x artifacts. Their code is not used by other Log4j components.

log4j-1.2-api

log4j-1.2-api contains a Log4j1ConfigurationConverter, which shares code with the old (and disabled) Log4j1ConfigurationFactory. IMHO:

• both components and their dependencies should be removed in 3.x,
• their functionality should be moved to a separate component (in a new repo or logging-log4j-transform).

Remark that the new configuration factory used by log4j-1.2-api is based on org.apache.log4j.builders and is extensible.
With some minor adjustments to the o.a.l.b.Builder interface we can switch Log4j1ConfigurationConverter to the new infrastructure and use it in openrewrite/rewrite-logging-frameworks#48.

log4j-core

Log4j Core contains a simple custom logger generator and an old copy of remkop/picocli. This should also be removed from the main code and transfered to a new artifact.

[vy]

I support the proposed log4j-1.2-api changes.

Log4j Core contains ... an old copy of remkop/picocli. This should also be ... transferred to a new artifact

Why do we create a log4j-picocli instead of using info.picocli:picocli?

[ppkarwasz]

@vy,

I meant to transfer the code that used Picocli to a new artifact and add info.picocli:picocli as a dependency.
Actually I have a branch for this issue, which is almost ready to be published.

I just don't know which repo should be used: a custom logger generator doesn't match the purpose of logging-log4j-transform, on the other hand logging-log4j-tools is for internal tools only.

[vy]

@ppkarwasz, if we are gonna totally remove it in 3.x, I think we can lay down the separate artifact to 2.x to rest in peace.

[ppkarwasz]

Closed in #2435