Move o.a.l.l.core.parser to samples

We move `o.a.l.l.core.parser` to the samples repository, since it is
independent from Log4j Core and unused:

apache/logging-log4j-samples@de33cee

This code is potentially (transitively) exploitable each time Jackson
has a deserialization vulnerability.

Part of #2016.

Author: ppkarwasz

log4j-core-test/src/main/java/org/apache/logging/log4j/core/test/parser/AbstractLogEventParserTest.java

@@ -115,12 +115,6 @@
       <artifactId>jackson-databind</artifactId>
       <optional>true</optional>
     </dependency>
-    <!-- Required for XML layout and receiver support -->
-    <dependency>
-      <groupId>com.fasterxml.jackson.dataformat</groupId>
-      <artifactId>jackson-dataformat-xml</artifactId>
-      <optional>true</optional>
-    </dependency>
     <!-- Required for YAML support (including JSON requirements) -->
     <dependency>
       <groupId>com.fasterxml.jackson.dataformat</groupId>