Make CI image to be configurable

[mordamax]

Context: paritytech/command-bot-scripts#37 (comment)
During the Rust version update, the source code of substrate repo should be gone through UI tests under specific Rust version + check if it is buildable with other pipelines
The rust version is defined by CI image, so CI team changes it manually in PR like this https://github.com/paritytech/substrate/pull/14422/files
Currently if you run Command-bot the CI image is hardcoded to be paritytech/ci-linux:production, but ideally should be the temporary CI_IMAGE with tested rust version.

Ideally the command-bot itself should be more generic and know nothing about particular org, while the environment should be defined by .cmd.js files

UPD:
Outcome: -v CMD_IMAGE=<image_name>
Example: bot update-ui -v CMD_IMAGE=paritytech/ci-unified:bullseye-1.70.0-2023-05-23 --rust_version=1.70.0