Generalize DI usage

This commit ensures that:

* an `InstanceFactory` is created in the Log4j `Provider`,
* the same factory is injected as parameters to all
  the components of the chain `Log4jContextFactory`, `ContextSelector`,
  `LoggerContext` (child), `Configuration` (grand-child).
* `DI.createInstanceFactory` is called only when strictly necessary.

Author: ppkarwasz

log4j-core/src/main/java/org/apache/logging/log4j/core/tools/Generate.java

@@ -62,7 +62,7 @@ String imports() {
                         + "import org.apache.logging.log4j.Marker;%n"
                         + "import org.apache.logging.log4j.message.Message;%n"
                         + "import org.apache.logging.log4j.message.MessageFactory;%n"
-                        + "import org.apache.logging.log4j.spi.AbstractLogger;%n"
+                        + "import org.apache.logging.log4j.spi.ExtendedLogger;%n"
                         + "import org.apache.logging.log4j.spi.ExtendedLoggerWrapper;%n"
                         + "import org.apache.logging.log4j.util.MessageSupplier;%n"
                         + "import org.apache.logging.log4j.util.Supplier;%n"
@@ -91,7 +91,7 @@ String constructor() {
                 return ""
                         + "%n"
                         + "    private %s(final Logger logger) {%n"
-                        + "        this.logger = new ExtendedLoggerWrapper((AbstractLogger) logger, logger.getName(), "
+                        + "        this.logger = new ExtendedLoggerWrapper((ExtendedLogger) logger, logger.getName(), "
                         + "logger.getMessageFactory());%n"
                         + "    }%n";
                 // @formatter:on
@@ -113,7 +113,7 @@ String imports() {
                         + "import org.apache.logging.log4j.Marker;%n"
                         + "import org.apache.logging.log4j.message.Message;%n"
                         + "import org.apache.logging.log4j.message.MessageFactory;%n"
-                        + "import org.apache.logging.log4j.spi.AbstractLogger;%n"
+                        + "import org.apache.logging.log4j.spi.ExtendedLogger;%n"
                         + "import org.apache.logging.log4j.spi.ExtendedLoggerWrapper;%n"
                         + "import org.apache.logging.log4j.util.MessageSupplier;%n"
                         + "import org.apache.logging.log4j.util.Supplier;%n"
@@ -143,7 +143,7 @@ String constructor() {
                 return ""
                         + "%n"
                         + "    private %s(final Logger logger) {%n"
-                        + "        super((AbstractLogger) logger, logger.getName(), logger.getMessageFactory());%n"
+                        + "        super((ExtendedLogger) logger, logger.getName(), logger.getMessageFactory());%n"
                         + "        this.logger = this;%n"
                         + "    }%n";
                 // @formatter:on