[RCS]Add getEncodedMessage() in SipMessage.java

    ctor public SipMessage(@NonNull String, @NonNull String, @NonNull byte[]);

    method public int describeContents();

    method @NonNull public byte[] getContent();

    method @NonNull public byte[] getEncodedMessage();

    method @NonNull public String getHeaderSection();

    method @NonNull public String getStartLine();

    method public void writeToParcel(@NonNull android.os.Parcel, int);

package android.telephony.ims;

import static java.nio.charset.StandardCharsets.UTF_8;

import android.annotation.NonNull;

import android.annotation.SystemApi;

import android.os.Build;

public final class SipMessage implements Parcelable {

    // Should not be set to true for production!

    private static final boolean IS_DEBUGGING = Build.IS_ENG;

    private static final String CRLF = "\r\n";

    private final String mStartLine;

    private final String mHeaderSection;

        result = 31 * result + Arrays.hashCode(mContent);

        return result;

    }

    /**

     * @return the UTF-8 encoded SIP message.

     */

    public @NonNull byte[] getEncodedMessage() {

        byte[] header = new StringBuilder()

                .append(mStartLine)

                .append(mHeaderSection)

                .append(CRLF)

                .toString().getBytes(UTF_8);

        byte[] sipMessage = new byte[header.length + mContent.length];

        System.arraycopy(header, 0, sipMessage, 0, header.length);

        System.arraycopy(mContent, 0, sipMessage, header.length, mContent.length);

        return sipMessage;

    }

}