feat: Include autoattach contexts when listing stack env

[tomasmik]

This is a bit confusing now, but I think this is the easiest way to not accidentally duplicate the information returned.

Name                            | Type                 | Value      | Context | IsAutoattached
SPACELIFT_API_TOKEN             | ENVIRONMENT_VARIABLE | <computed> |         |
SPACELIFT_OIDC_TOKEN            | ENVIRONMENT_VARIABLE | <computed> |         |
TF_VAR_spacelift_account_name   | ENVIRONMENT_VARIABLE | <computed> |         |
...
bbbb                            | ENVIRONMENT_VARIABLE | bbb        | aaa     | false
vvv                             | ENVIRONMENT_VARIABLE | aaa        |         |
aaa                             | ENVIRONMENT_VARIABLE | aaa        | asdf111 | true

This is a result for a stack that has a context bbbb attached, aaa auto-attached and vvv set as a normal variable.

[spr-mweber3]

Fixes #271 ...

Thanks for that!