It's now valid to include an oci_mirror block in the provider_installation
block in the CLI configuration, specifying that OpenTofu should try to
install providers from OCI repositories based on a template that maps
from OpenTofu-style provider source addresses into OCI repository
addresses.
The getproviders.Source implementation for this was added in a previous
commit, so this is mainly just wiring it up to the cliconfig layer and
the dependency wiring code in package main.
Signed-off-by: Martin Atkins <mart@degeneration.co.uk>
6dab83e3bc