Kotlin conversion: KeyIdUtil

This PR also introduces LongExtensions.kt which provides extension methods to
parse Long from Hex KeyIDs and to format Longs as Hex KeyIDs.

pgpainless-core/src/main/kotlin/org/pgpainless/key/util/KeyIdUtil.kt

@@ -0,0 +1,36 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.key.util
+
+import _kotlin.fromHexKeyId
+import _kotlin.hexKeyId
+
+class KeyIdUtil {
+
+    companion object {
+
+        /**
+         * Convert a long key-id into a key-id.
+         * A long key-id is a 16 digit hex string.
+         *
+         * @param longKeyId 16-digit hexadecimal string
+         * @return key-id converted to {@link Long}.
+         */
+        @JvmStatic
+        @Deprecated("Superseded by Long extension method.",
+                ReplaceWith("Long.fromHexKeyId(longKeyId)"))
+        fun fromLongKeyId(longKeyId: String) = Long.fromHexKeyId(longKeyId)
+
+        /**
+         * Format a long key-ID as upper-case hex string.
+         * @param keyId keyId
+         * @return hex encoded key ID
+         */
+        @JvmStatic
+        @Deprecated("Superseded by Long extension method.",
+                ReplaceWith("keyId.hexKeyId()"))
+        fun formatKeyId(keyId: Long) = keyId.hexKeyId()
+    }
+}