When a resource has no `provider` argument specified, its provider is
derived from the implied provider type based on the resource type. For
example, a `boop_instance` resource has an implied provider local name
of `boop`. Correspondingly, its provider configuration is specified with
a `provider "boop"` block.
However, users can use the `required_providers` configuration to give a
different local name to a given provider than its defined type. For
example, a provider may be published at `foobar/beep`, but provide
resources such as `boop_instance`. The most convenient way to use this
provider is with a `required_providers` map:
terraform {
required_providers {
boop = {
source = "foobar/beep"
}
}
}
Once that local name is defined, it is used for provider configuration
(a `provider "boop"` block, not `provider "beep"`). It should also be
used when looking up a resource's provider configuration or provider.
This commit fixes a bug with this edge case, where previously we were
looking up the local provider configuration block using the resource's
assigned provider type. Instead, if no provider argument is specified,
we should be using the implied provider type, as that is what binds the
resource to the local provider configuration.
