Inconsistent json output of env show command

[hoesler]

I identified two inconsistencies when using the --json flag in the hatch env show subcommand:

1. The json object contains all envs if the envs arg is passed for selecting specific envs.
2. For matrix envs, the json object contains no explicit information about the matrix an env belongs to (i.e. the matrix name).

I will open a PR to address this issue.

[ofek]

I'd be happy to discuss further in a PR!