OmegaConf.resolve cannnot resolve a dictionary

[miaopas]

Describe the bug
For a custom resolver that returns a dictionary, OmegaConf.resolve report error, but other functions like OmegaConf.to_container(cfg, resolve=True) will work

To Reproduce

OmegaConf.register_new_resolver('foo', lambda x: {x: 1}, replace=True)

c = """
key1: poly # (smooth, nonsmooth)
key2: ${foo:${key1}}
"""
cfg = OmegaConf.create(c)

# Works
OmegaConf.to_container(cfg, resolve=True) 

# Not working
OmegaConf.resolve(cfg)

Expected behavior
OmegaConf.resolve should also work in this case?

Additional context

• OmegaConf version: 2.3.0
• Python version: 3.10.12
• Operating system: Ubuntu 22.04.4
• Please provide a minimal repro