NXCON-277: Modernize CI/CD, auto-derive release version, streamline build & release workflows

This change consolidates the CI pipeline by:

-> Converting build_and_test.yml from a reusable workflow_call workflow to a standalone workflow triggered directly on push/PR.
-> Deleting the caller workflows pipeline_pr.yaml and pipeline_release.yml.
-> Adding a new release.yml for automated release orchestration.
-> Adding a dedicated .github/maven-settings.xml file (replacing inline XML generation).

Author: abhishek-gupta-nuxeo

.github/maven-settings.xml

@@ -0,0 +1,32 @@
+<settings>
+    <mirrors>
+        <mirror>
+            <id>maven-internal-build</id>
+            <name>Internal Group having all Maven Repositories</name>
+            <url>https://packages.nuxeo.com/repository/maven-internal-build</url>
+            <mirrorOf>*,!nuxeo-studio,!maven-internal</mirrorOf>
+        </mirror>
+    </mirrors>
+    <servers>
+        <server>
+            <id>maven-internal-build</id>
+            <username>${env.MVN_REPO_USERNAME}</username>
+            <password>${env.MVN_REPO_PASSWORD}</password>
+        </server>
+        <server>
+            <id>maven-internal</id>
+            <username>${env.MVN_REPO_USERNAME}</username>
+            <password>${env.MVN_REPO_PASSWORD}</password>
+        </server>
+        <server>
+            <id>maven-public-snapshots</id>
+            <username>${env.MVN_REPO_USERNAME}</username>
+            <password>${env.MVN_REPO_PASSWORD}</password>
+        </server>
+        <server>
+            <id>maven-public-releases</id>
+            <username>${env.MVN_REPO_USERNAME}</username>
+            <password>${env.MVN_REPO_PASSWORD}</password>
+        </server>
+    </servers>
+</settings>