Replace ${sys:PID} with %pid in log4j2 configuration

Replacing property sys:PID which was set in the code with the default
log4j2 Pattern in log4j2.xml and log4j2-file.xml files.

Closes gh-16174

spring-boot-project/spring-boot/src/main/resources/org/springframework/boot/logging/log4j2/log4j2-file.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <Configuration status="WARN">
 	<Properties>
-		<Property name="PID">????</Property>
 		<Property name="LOG_EXCEPTION_CONVERSION_WORD">%xwEx</Property>
 		<Property name="LOG_LEVEL_PATTERN">%5p</Property>
 		<Property name="LOG_DATEFORMAT_PATTERN">yyyy-MM-dd HH:mm:ss.SSS</Property>
-		<Property name="CONSOLE_LOG_PATTERN">%clr{%d{${LOG_DATEFORMAT_PATTERN}}}{faint} %clr{${LOG_LEVEL_PATTERN}} %clr{${sys:PID}}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
-		<Property name="FILE_LOG_PATTERN">%d{${LOG_DATEFORMAT_PATTERN}} ${LOG_LEVEL_PATTERN} ${sys:PID} --- [%t] %-40.40c{1.} : %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
+		<Property name="CONSOLE_LOG_PATTERN">%clr{%d{${LOG_DATEFORMAT_PATTERN}}}{faint} %clr{${LOG_LEVEL_PATTERN}} %clr{%pid}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
+		<Property name="FILE_LOG_PATTERN">%d{${LOG_DATEFORMAT_PATTERN}} ${LOG_LEVEL_PATTERN} %pid --- [%t] %-40.40c{1.} : %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
 
 	</Properties>
 	<Appenders>

spring-boot-project/spring-boot/src/main/resources/org/springframework/boot/logging/log4j2/log4j2.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <Configuration status="WARN">
 	<Properties>
-		<Property name="PID">????</Property>
 		<Property name="LOG_EXCEPTION_CONVERSION_WORD">%xwEx</Property>
 		<Property name="LOG_LEVEL_PATTERN">%5p</Property>
 		<Property name="LOG_DATEFORMAT_PATTERN">yyyy-MM-dd HH:mm:ss.SSS</Property>
-		<Property name="CONSOLE_LOG_PATTERN">%clr{%d{${LOG_DATEFORMAT_PATTERN}}}{faint} %clr{${LOG_LEVEL_PATTERN}} %clr{${sys:PID}}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
-		<Property name="FILE_LOG_PATTERN">%d{${LOG_DATEFORMAT_PATTERN}} ${LOG_LEVEL_PATTERN} ${sys:PID} --- [%t] %-40.40c{1.} : %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
+		<Property name="CONSOLE_LOG_PATTERN">%clr{%d{${LOG_DATEFORMAT_PATTERN}}}{faint} %clr{${LOG_LEVEL_PATTERN}} %clr{%pid}{magenta} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
+		<Property name="FILE_LOG_PATTERN">%d{${LOG_DATEFORMAT_PATTERN}} ${LOG_LEVEL_PATTERN} %pid --- [%t] %-40.40c{1.} : %m%n${sys:LOG_EXCEPTION_CONVERSION_WORD}</Property>
 	</Properties>
 	<Appenders>
 		<Console name="Console" target="SYSTEM_OUT" follow="true">