[V3 Config] Adjust functionality of get_attr

[tekulvw]

This is a BREAKING CHANGE

Type

• Bugfix
• Enhancement
• New feature

Description of the changes

For a bit of background: get_attr has a resolve kwarg which changes how the method acts. If resolve is true, get_attr will return a coroutine which, when awaited, returns the actual saved value of that attribute. If resolve is false, get_attr returns the next nested group object

As an example:

conf.get_attr('test', resolve=False)
# is equivalent to
conf.test

And:

await conf.get_attr('test', resolve=True)
# is equivalent to
await conf.test()

And:

await conf.get_attr('test', resolve=True)
# is equivalent to
await conf.get_raw('test')

This PR permanently removes the resolve kwarg from get_attr and keeps the functionality that occurs when resolve=False is passed currently.

set_attr was also removed.

This change was brought on by it's replacement by set_raw.