Show current config on config screen. Load default config if config unset

- Track current (saved/loaded) config separate from the new config (to
  be written) when user clicks Start

- Fallback to using default config when no config for the specific
  content type or processor is specified in khoj.yml
  - Earlier were only loading default config on first run, not after

- Create Child CheckBox, LineEdit classes for Processor Widgets
  - Create ProcessorType, similar to SearchType
  - Track ProcessorType the widgets are associated with
  - Simplify update, save, load of config based on type

src/utils/config.py

@@ -15,6 +15,10 @@ class SearchType(str, Enum):
     Image = "image"
 
 
+class ProcessorType(str, Enum):
+    Conversation = "conversation"
+
+
 class TextSearchModel():
     def __init__(self, entries, corpus_embeddings, bi_encoder, cross_encoder, top_k, verbose):
         self.entries = entries