Accept float values for --max-fps

Android accepts a float value, there is no reason to limit the option
to be an integer.

In particular, it allows to capture at a rate lower than 1 fps. For
example, to capture 1 frame every 5 seconds:

    scrcpy --video-source=camera --max-fps=0.2

It was already possible to pass a float manually:

    scrcpy --video-source=camera \
        --video-codec-options=max-fps-to-encoder:float=0.2

But accepting a float directly for --max-fps is more convenient.

Refs <https://developer.android.com/reference/android/media/MediaFormat#KEY_MAX_FPS_TO_ENCODER>

app/src/cli.c

@@ -1447,6 +1447,26 @@ parse_integers_arg(const char *s, const char sep, size_t max_items, long *out,
     return count;
 }
 
+static bool
+parse_float_arg(const char *s, float *out, float min, float max,
+                const char *name) {
+    float value;
+    bool ok = sc_str_parse_float(s, &value);
+    if (!ok) {
+        LOGE("Could not parse %s: %s", name, s);
+        return false;
+    }
+
+    if (value < min || value > max) {
+        LOGE("Could not parse %s: value (%f) out-of-range (%f; %f)",
+             name, value, min, max);
+        return false;
+    }
+
+    *out = value;
+    return true;
+}
+
 static bool
 parse_bit_rate(const char *s, uint32_t *bit_rate) {
     long value;
@@ -1474,14 +1494,14 @@ parse_max_size(const char *s, uint16_t *max_size) {
 }
 
 static bool
-parse_max_fps(const char *s, uint16_t *max_fps) {
-    long value;
-    bool ok = parse_integer_arg(s, &value, false, 0, 0xFFFF, "max fps");
+parse_max_fps(const char *s, float *max_fps) {
+    float value;
+    bool ok = parse_float_arg(s, &value, 0, (float) (1 << 16), "max fps");
     if (!ok) {
         return false;
     }
 
-    *max_fps = (uint16_t) value;
+    *max_fps = value;
     return true;
 }