feat(server): transcode bitrate and thread settings (#2488)

* support for two-pass transcoding

* added max bitrate and thread to transcode api

* admin page setting desc+bitrate and thread options

* Update web/src/lib/components/admin-page/settings/setting-input-field.svelte

Co-authored-by: Michel Heusschen <59014050+michelheusschen@users.noreply.github.com>

* Update web/src/lib/components/admin-page/settings/setting-input-field.svelte

Co-authored-by: Michel Heusschen <59014050+michelheusschen@users.noreply.github.com>

* two-pass slider, `crf` and `threads` as numbers

* updated and added transcode tests

* refactored `getFfmpegOptions`

* default `threads`, `maxBitrate` now 0, more tests

* vp9 constant quality mode

* fixed nullable `crf` and `threads`

* fixed two-pass slider, added apiproperty

* optional `desc` for `SettingSelect`

* disable two-pass if settings are incompatible

* fixed test

* transcode interface

---------

Co-authored-by: Michel Heusschen <59014050+michelheusschen@users.noreply.github.com>

server/libs/domain/test/fixtures.ts

@@ -479,11 +479,14 @@ export const keyStub = {
 export const systemConfigStub = {
   defaults: Object.freeze({
     ffmpeg: {
-      crf: '23',
+      crf: 23,
+      threads: 0,
       preset: 'ultrafast',
       targetAudioCodec: 'aac',
       targetResolution: '720',
       targetVideoCodec: 'h264',
+      maxBitrate: '0',
+      twoPass: false,
       transcode: TranscodePreset.REQUIRED,
     },
     oauth: {