Migrate build infrastructure from Gradle to Maven

- Add pom.xml with all dependencies, compiler settings (Java 1.8, -parameters),
  jar manifest (Automatic-Module-Name), javadoc, source, and GPG signing profile
- Add Maven wrapper (mvnw/mvnw.cmd) replacing Gradle wrapper
- Rename gradle-build.yml to maven-build.yml with Maven commands and cache
- Update codeql-analysis.yml to use mvnw compile
- Update ADO ci-build.yml with Maven install/deploy and settings.xml auth
- Update ADO daily-ci-build.yml with Maven@4 task and network-isolated mirror
- Update dependabot.yml: maven ecosystem for root, gradle kept for /android
- Update .gitignore: swap Gradle entries for Maven
- Update release-please-config.json: XML xpath updater for pom.xml version
- Inline dependencies into android/build.gradle (remove shared gradle/dependencies.gradle)
- Remove all root Gradle files and java-8/ sub-project

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: ramsessanchez

.github/workflows/gradle-build.yml .github/workflows/maven-build.yml.github/workflows/gradle-build.yml renamed to .github/workflows/maven-build.yml

@@ -0,0 +1,2 @@
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.9/apache-maven-3.9.9-bin.zip
+wrapperUrl=https://repo.maven.apache.org/maven2/org/apache/maven/wrapper/maven-wrapper/3.3.2/maven-wrapper-3.3.2.jar