[bug][docs] Missing information about removal of `-e`, `-e:b` and `-e:h` and what to use instead

With Conan 2 the `-e`, `-e:b` and `-e:h` parameters was removed:
* https://docs.conan.io/2/reference/commands/install.html#conan-install
* https://docs.conan.io/1/reference/commands/consumer/install.html
* https://github.com/conan-io/conan/blob/59029095e86eacd402083fca7c308b06889f6301/conan/cli/args.py#L35

There is missing information in documentation about it (e.g. in migration guide: https://docs.conan.io/1/migrating_to_2.0/general.html#environment-variables) and how to replace it.