Fix build errors and warnings

[fmbenhassine]

After the migration to Maven, the build started showing some errors and warnings:

07:11:51,862 |-ERROR in ch.qos.logback.classic.PatternLayout("") - Empty or null pattern.

v4 should be released with a warning free clean build.

[fmbenhassine]

[INFO] --- maven-compiler-plugin:3.14.1:compile (default-compile) @ spring-shell-core ---
[INFO] Recompiling the module because of changed source code.
[INFO] Compiling 59 source files with javac [debug release 17] to target/classes
[WARNING] /Users/mbh/projects/spring-shell/spring-shell-core/src/main/java/org/springframework/shell/core/JnaRuntimeHints.java:[65,56] DECLARED_CLASSES in org.springframework.aot.hint.MemberCategory has been deprecated and marked for removal
[WARNING] /Users/mbh/projects/spring-shell/spring-shell-core/src/main/java/org/springframework/shell/core/JnaRuntimeHints.java:[65,89] DECLARED_FIELDS in org.springframework.aot.hint.MemberCategory has been deprecated and marked for removal
[WARNING] /Users/mbh/projects/spring-shell/spring-shell-core/src/main/java/org/springframework/shell/core/JnaRuntimeHints.java:[66,55] PUBLIC_CLASSES in org.springframework.aot.hint.MemberCategory has been deprecated and marked for removal
[WARNING] /Users/mbh/projects/spring-shell/spring-shell-core/src/main/java/org/springframework/shell/core/JnaRuntimeHints.java:[66,86] PUBLIC_FIELDS in org.springframework.aot.hint.MemberCategory has been deprecated and marked for removal