Feature request - Allow to set multiple config variables in one "bundle config" call

Describe the problem as clearly as you can

Here is my understanding:

• Since Bundler 2.1+, --path, --without and --deployment options are deprecated in a given bundler install
• This resulted in adaptation for deployment tooling (for instance https://github.com/capistrano/bundler/pull/122/files, but also other private stuff) with 3 bundle config --local calls
• This increases deployment / CI-CD deployment time (sometimes by ~ 10 seconds if you are on a slow setup, or on JRuby)
• I do understand that ENV variables could be used to work-around this (in Capistrano-bundler or similar tooling), but usually it is less explicit (defined a bit further away for instance)

Hence I wonder if bundler config could be made to allow configuring N variables in one go, to accelerate this & save resources, without resorting to ENV variables.

Start by tracing the existing bundle config command and how it accepts and persists configuration values. Review the deployment examples linked in the issue to understand the intended multi-variable invocation. Done means one bundle config call can set multiple variables while preserving the current configuration behavior.