(core) Refactor more value parsing code into common

Summary:
Following discussion in https://phab.getgrist.com/D3164:

- Change createParser to accept docData and one or two metadata row IDs and let it extract the metadata, so it's more easily usable in the server.
- Change ViewFieldRec.valueParser observable to a function createValueParser.

Test Plan: Existing tests.

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D3172

app/client/widgets/NTextEditor.ts

@@ -76,7 +76,7 @@ export class NTextEditor extends NewBaseEditor {
   }
 
   public getCellValue(): CellValue {
-    const valueParser = this.options.field.valueParser.peek();
+    const valueParser = this.options.field.createValueParser();
     return valueParser(this.getTextValue());
   }