[hailctl] Add list command to dump parts of user config (#9529)
[hailctl] Add list command to dump parts of user config (#9529)

Syntax: hailctl config list [section]

Output:
```
with no section specified:
{section}/{key}={value}
with a section specified:
{key}={value}
```
hail-is/hail,danking/hail,cseed/hail,cseed/hail,hail-is/hail,cseed/hail,cseed/hail,danking/hail,hail-is/hail,cseed/hail,cseed/hail,hail-is/hail,hail-is/hail,cseed/hail,danking/hail,danking/hail,danking/hail,hail-is/hail,cseed/hail,danking/hail,hail-is/hail,danking/hail,danking/hail,hail-is/hail