Use X509ExtendedTrustManager to avoid JDK AlgorithmChecker constraints

Netty 4.2.15 fixed CVE-2026-50010 by removing the silent wrapping of
plain X509TrustManager in X509ExtendedTrustManager. When a plain
X509TrustManager is used, the JDK wraps it in AbstractTrustManagerWrapper
and runs TrustManagerImpl.checkTrusted() with AlgorithmChecker before
calling the custom trust manager.

This caused client certificates signed with SHA3-512withECDSA to be
rejected even though they are not explicitly blacklisted in java.security,
because the JDK's internal PKIX validator applies stricter constraints.

By making our custom trust managers implement X509ExtendedTrustManager
directly, the JDK calls the 3-arg methods directly and bypasses its
internal TrustManagerImpl, restoring the pre-4.2.15 behavior where
only our custom PKIX validation runs.

Files changed:
- rbcs-common/RBCS.kt: getTrustManager() returns X509ExtendedTrustManager
- rbcs-client/RemoteBuildCacheClient.kt: trust-all manager uses X509ExtendedTrustManager

rbcs-cli/native-image/native-image.properties

@@ -2,7 +2,7 @@ Args=-O3 \
    -march=x86-64-v3 \
    --gc=serial \
    --enable-url-protocols=jpms \
-   --pgo=conf/default.iprof \
+   --pgo=native-image/default.iprof \
    --initialize-at-run-time=io.netty \
    --initialize-at-build-time=net.woggioni.rbcs.common.RbcsUrlStreamHandlerFactory,net.woggioni.rbcs.common.RbcsUrlStreamHandlerFactory$JpmsHandler \
    --trace-object-instantiation=ch.qos.logback.classic.Logger \

settings.gradle

@@ -1,5 +1,12 @@
 pluginManagement {
     repositories {
+//        mavenLocal {
+//            content {
+//                includeGroup 'net.woggioni.gradle'
+//                includeGroup 'net.woggioni.gradle.lombok'
+//                includeGroup 'net.woggioni.gradle.finalguard'
+//            }
+//        }
         maven {
             url = getProperty('gitea.maven.url')
         }