Rename --no-mirror to --no-playback

This option impacts video and audio _playback_. For example, if we use
V4L2, the device is still "mirrored" (via V4L2), even if playback is
disabled. Therefore, "playback" is more approriate than "mirror".

The initial option --no-display option was renamed to --no-mirror by
commit 6928acdeac, but this has never been
released, so it is ok to rename it one more time.

Refs #3978 <https://github.com/Genymobile/scrcpy/pull/3978#issuecomment-1549420103>
PR #4033 <https://github.com/Genymobile/scrcpy/pull/4033>

app/tests/test_cli.c

@@ -53,7 +53,7 @@ static void test_options(void) {
         "--max-size", "1024",
         "--lock-video-orientation=2", // optional arguments require '='
         // "--no-control" is not compatible with "--turn-screen-off"
-        // "--no-mirror" is not compatible with "--fulscreen"
+        // "--no-playback" is not compatible with "--fulscreen"
         "--port", "1234:1236",
         "--push-target", "/sdcard/Movies",
         "--record", "file",
@@ -108,8 +108,8 @@ static void test_options2(void) {
     char *argv[] = {
         "scrcpy",
         "--no-control",
-        "--no-mirror",
-        "--record", "file.mp4", // cannot enable --no-mirror without recording
+        "--no-playback",
+        "--record", "file.mp4", // cannot enable --no-playback without recording
     };
 
     bool ok = scrcpy_parse_args(&args, ARRAY_LEN(argv), argv);
@@ -117,7 +117,7 @@ static void test_options2(void) {
 
     const struct scrcpy_options *opts = &args.opts;
     assert(!opts->control);
-    assert(!opts->mirror);
+    assert(!opts->playback);
     assert(!strcmp(opts->record_filename, "file.mp4"));
     assert(opts->record_format == SC_RECORD_FORMAT_MP4);
 }