Additional json output for mise doctor and mise env

[hverlin]

Hi, would it be possible to add json output for more commands?

• mise doctor --json (this would allow one to extract settings, dirs, warnings, ...)
• mise env --json exists, however it does not indicate which config file was used to load each environment variable (like mis ls --json or mise tasks --json). Can we add another option to this command to indicate where the variable comes from?