Respect $XDG_CONFIG_HOME and add --config overwrite for config path

[feedmeapples]

Is your feature request related to a problem? Please describe.

Currently config file location is enforced to UserHomeDir()/.config/temporalio/tctl.yml and doesn't allow to have a different location

Describe the solution you'd like

Respect XDG_CONFIG_HOME env variable
Allow users to overwrite with --config flag

Additional context

current config file location:

cat ~/.config/temporalio/tctl.yaml

the actual config file location code lives here https://github.com/temporalio/tctl-kit