Can't upgrade provider from non-tagged version

[danielrbradley]

If the provider currently depends on a version of the upstream terraform provider which is not tagged but is a pseudo-version of a specific commit hash, upgrade provider will fail with a message such as:

go.mod

github.com/pulumi/terraform-provider-xyz v0.0.0-20241101124823-179d09f02e1f

Upgrade provider error

error: no tag commit that matched '179d09f02e1f' in 'https://github.com/pulumi/terraform-provider-xyz.git'

If we're not on a tagged version, we should use the pseudo-version to infer the approximate current version for the baseline to upgrade from.