Add basic JUL to Log4j API conversion

[ppkarwasz]

What's changed?

This PR converts the most commonly used JUL methods to their Log4j API equivalents:

• Logger#getLogger,
• all Logger#<logging_level methods,
• Logger#entering,
• Logger#exiting.

What's your motivation?

This is part of our apache/logging-log4j2#2080 task. The main motivation is a user request for support (cf. apache/logging-log4j2#2083), hence the implementation of the entering/exiting rules.

Closes #132

Checklist

• [x] I've added unit tests to cover both positive and negative cases
• [x] I've read and applied the recipe conventions and best practices
• [x] I've used the IntelliJ IDEA auto-formatter on affected files