(core) Remove REPL code

Summary: Remove repl.py, REPLTab.js, some wiring code, CSS, and a test in testscript.json.

Test Plan: NA

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2923

app/common/UserConfig.ts

@@ -25,6 +25,5 @@ export interface ISupportedFeatures {
   // Plugin views, REPL, and Validations all need work, but are exposed here to allow existing
   // tests to continue running. These only affect client-side code.
   customViewPlugin?: boolean;
-  replTool?: boolean;
   validationsTool?: boolean;
 }