(core) One more phase of ACL UI revision.

Summary:
- Add ACLColumnList widget for a list of column IDs.
- Replace autocomplete widgets with simpler dropdowns.
- Add select dropdown for the Attribute of UserAttribute rules.
- Switch formula to use ACE editor.
- Factor out customized completion logic from AceEditor.js into a separate file.
- Implement completions for ACL formulas.
- Collect ACL UI files in app/client/aclui

Test Plan: Updated test case, some behavior (like formula autocomplete) only tested manually.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2697

app/client/ui2018/icons.ts

@@ -87,7 +87,7 @@ export const cssIconButton = styled('div', `
   line-height: 0px;
   cursor: default;
   --icon-color: ${colors.slate};
-  &:hover {
+  &:hover, &.weasel-popup-open {
     background-color: ${colors.darkGrey};
     --icon-color: ${colors.slate};
   }