fix(attestation): encode PADDING as SET OF INTEGER per AOSP schema

PADDING (tag 6) is ENUM_REP in Tag.aidl, meaning SET OF INTEGER in the
attestation extension ASN.1, same as PURPOSE and DIGEST. Commit 1fa6f5a
added it as individual [6] INTEGER entries, causing parsers to fail with
CertificateParsingException on any RSA key attestation.

app/src/main/java/org/matrix/TEESimulator/attestation/AttestationBuilder.kt

@@ -194,9 +194,13 @@ object AttestationBuilder {
             )
         }
 
-        params.padding.forEach {
+        if (params.padding.isNotEmpty()) {
             list.add(
-                DERTaggedObject(true, AttestationConstants.TAG_PADDING, ASN1Integer(it.toLong()))
+                DERTaggedObject(
+                    true,
+                    AttestationConstants.TAG_PADDING,
+                    DERSet(params.padding.map { ASN1Integer(it.toLong()) }.toTypedArray()),
+                )
             )
         }