fix: preserve reserved keyword in module import diagnostic message

When a reserved keyword (e.g. 'client') is used in a module import path
without the '^' escape prefix, BLangIdentifier.value is empty string
while originalValue holds the raw source text.

getQualifiedPackageName() was using id.value for all identifiers, causing
the keyword to be silently dropped and producing misleading diagnostics
like 'cannot resolve module ballerinax/.config' instead of the correct
'cannot resolve module ballerinax/client.config'.

Fall back to originalValue when value is empty to preserve the keyword
in the diagnostic message.

Fixes: #44509, #44519

Author: notdulain

compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/tree/BLangImportPackage.java

@@ -134,7 +134,7 @@ public String toString() {
     public String getQualifiedPackageName() {
         String orgName = this.orgName.toString();
         String pkgName = String.join(".", pkgNameComps.stream()
-                .map(id -> id.value)
+                .map(id -> id.value.isEmpty() && id.originalValue != null ? id.originalValue : id.value)
                 .toList());
 
         String versionStr = (this.version.value != null) ? this.version.value : "";