Migrate to Maven Central Portal and fix CI memory issues

- Replace nexus-staging-maven-plugin with central-publishing-maven-plugin 0.9.0
- Add maven-source-plugin to generate required sources JAR for Central Portal
- Remove deprecated distributionManagement section
- Add -Dforce.fast=true to GitLab CI to avoid memory issues with JFlex DFA generation

Change-Id: Idd8d5b2d6a2713d93fb0d18429e7d73a7b68f021
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f1f7a14..72c5791 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -14,7 +14,7 @@
 build:
   stage: build
   script:
-    - mvn $MAVEN_CLI_OPTS clean package
+    - mvn $MAVEN_CLI_OPTS clean package -Dforce.fast=true
   artifacts:
     paths:
       - target/KorAP-Tokenizer-*-standalone.jar