ffmpeg -i 参数支持url

原流程：非本机存储需要先下载完整视频文件到cloudreve服务端 存储到临时目录 再获取缩略图
忧化后：直接读取视频url元数据后 获取缩略图（不需要读取视频整个文件，文件存储端 需要支持range）
ffmpegOpts["thumb_ffmpeg_path"], "-ss", ffmpegOpts["thumb_ffmpeg_seek"], "-i", tempInputPath, "-vf", scaleOpt, "-vframes", "1", tempOutputPath)
ffmpeg命令行执行代码中，只需要 tempInputPath 换成 视频URL地址，不需要变更/增加其它参数

6372984 -rwxr--r-- 1 root root 6525927788 Aug 14 00:33 AiwonviV_test.mp4
一个6G 的文件 只需要3s即可获取到视频第一帧，改成url网络地址后 ，文件大小限制可以不受 cloudreve磁盘大小影响(最大原始文件1GB的限制)，也节省了中转到cr服务端的视频文件流量

` Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
creation_time : 2023-01-01T03:30:57.000000Z
encoder : Lavf59.34.101
Duration: 04:23:48.75, start: 0.000000, bitrate: 3298 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 3101 kb/s, 24.83 fps, 25 tbr, 90k tbn, 50 tbc (default)
Metadata:
creation_time : 2023-01-01T03:30:57.000000Z
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 188 kb/s (default)
Metadata:
creation_time : 2023-01-01T03:30:57.000000Z
handler_name : SoundHandler
Stream #0:2: Video: png, pal8(pc), 250x100, 90k tbr, 90k tbn, 90k tbc (attached pic)
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> mjpeg (native))
Press [q] to stop, [?] for help
[swscaler @ 0x555f4991f680] deprecated pixel format used, make sure you did set range correctly
Output #0, image2, to 'output_frame.jpg':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.45.100
Stream #0:0(und): Video: mjpeg, yuvj420p(pc), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc (default)
Metadata:
creation_time : 2023-01-01T03:30:57.000000Z
handler_name : VideoHandler
encoder : Lavc58.91.100 mjpeg
Side data:
cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
frame= 1 fps=0.0 q=5.4 Lsize=N/A time=00:00:00.04 bitrate=N/A speed=0.0936x
video:65kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

real 0m3.499s
user 0m0.776s
sys 0m0.135s`