fix: Create directories from envs_dirs if they do not exist

[holzman]

Fixes #3790

[holzman]

Ah, my bad. I'll revise the failing tests and update this PR.

[holzman]

Actually, I think this exposed an issue with #3692:

In 2.0.5, -r took precedence over MAMBA_ROOT_PREFIX:

$ export MAMBA_ROOT_PREFIX=/tmp/envroot
$ mamba create  --debug -n foo --print-config-only | yq '. | .envs_dirs'
[
  "/tmp/envroot/envs"
]

$ mamba create -r /tmp/cliroot --debug -n foo --print-config-only | yq '. | .envs_dirs'
[
  "/tmp/cliroot/envs"
]

but in 2.0.6:

$ mamba create -r /tmp/cliroot --debug -n foo --print-config-only | yq '. | .envs_dirs'
[
  "/tmp/envroot/envs",
  "/tmp/cliroot/envs"
]