CAMEL-23265 Fix unchecked/unsafe operations warning in camel-spring-boot-generator-maven-plugin

[cunningt]

Getting unchecked/unsafe operation warnings in camel-spring-boot-generator-maven-plugin - the error is from how the results from loadClass are consumed by addAnnotation

Add a loadAnnotationClass that uses proper typing for loading the Annotation class and use it in the one instance that we call addAnnotation.

BEFORE :

[INFO] /Users/tcunning/src/community/camel-spring-boot/tooling/camel-spring-boot-generator-maven-plugin/src/main/java/org/apache/camel/springboot/maven/SpringBootAutoConfigurationMojo.java: /Users/tcunning/src/community/camel-spring-boot/tooling/camel-spring-boot-generator-maven-plugin/src/main/java/org/apache/camel/springboot/maven/SpringBootAutoConfigurationMojo.java uses unchecked or unsafe operations.
[INFO] /Users/tcunning/src/community/camel-spring-boot/tooling/camel-spring-boot-generator-maven-plugin/src/main/java/org/apache/camel/springboot/maven/SpringBootAutoConfigurationMojo.java: Recompile with -Xlint:unchecked for details.

AFTER :

No unchecked or unsafe operation warning.