ANTLR 4 depends on node >= 14 which breaks bf-generate #1060

Versions

@microsoft/botframework-cli/4.11.0 win32-x64 node-v12.16.1
Windows

Describe the bug

@microsoft/bf-lu was changed to use Antlr4 rather than Antlr4ts which is what the SDK uses. This introduces a dependency on node >= 14 which conflicts with composer's node >= 12. This happens because bf-generate uses the cli LU parser in the CLI to do merges.

To Reproduce

Steps to reproduce the behavior:

1. npm config set Microsoft (@microsoft):registry https://botbuilder.myget.org/F/botframework-cli/npm/
   npm config set registry https://botbuilder.myget.org/F/botbuilder-v4-js-daily/npm/
2. bf plugins:install @microsoft/bf-generate

Expected behavior

Plugin should install. In actuality you get this error:
error antlr4@4.9.0: The engine "node" is incompatible with this module. Expected version ">=14". Got "12.16.1"
error Found incompatible module.

[bug]