Improve image scanning performance and thumbnail generation (#1655)

* Improve image scanning performance and thumbnail generation
* Add vips-tools to build image
* Add option to write generated thumbnails to disk
* Fallback to image if thumbnail generation fails

Co-authored-by: WithoutPants <53250216+WithoutPants@users.noreply.github.com>

graphql/documents/data/config.graphql

@@ -18,6 +18,7 @@ fragment ConfigGeneralData on ConfigGeneralResult {
   previewPreset
   maxTranscodeSize
   maxStreamingTranscodeSize
+  writeImageThumbnails
   apiKey
   username
   password

graphql/schema/types/config.graphql

@@ -63,6 +63,8 @@ input ConfigGeneralInput {
   maxTranscodeSize: StreamingResolutionEnum
   """Max streaming transcode size"""
   maxStreamingTranscodeSize: StreamingResolutionEnum
+  """Write image thumbnails to disk when generating on the fly"""
+  writeImageThumbnails: Boolean
   """Username"""
   username: String
   """Password"""
@@ -136,6 +138,8 @@ type ConfigGeneralResult {
   maxTranscodeSize: StreamingResolutionEnum
   """Max streaming transcode size"""
   maxStreamingTranscodeSize: StreamingResolutionEnum
+  """Write image thumbnails to disk when generating on the fly"""
+  writeImageThumbnails: Boolean!
   """API Key"""
   apiKey: String!
   """Username"""

graphql/schema/types/metadata.graphql

@@ -47,6 +47,8 @@ input ScanMetadataInput {
   scanGenerateSprites: Boolean
   """Generate phashes during scan"""
   scanGeneratePhashes: Boolean
+  """Generate image thumbnails during scan"""
+  scanGenerateThumbnails: Boolean
 }
 
 input CleanMetadataInput {