feat: Adds support for OIDC `WORKLOAD` IdP type to `federated_settings_identity_provider`

Description

Adds support for OIDC Workload IdPs for mongodbatlas_federated_settings_identity_provider

Link to any related issue(s): CLOUDP-250915

[ ] Bug fix (non-breaking change which fixes an issue). Please, add the "bug" label to the PR.
[ ] New feature (non-breaking change which adds functionality). Please, add the "enhancement" label to the PR. A migration guide must be created or updated if the new feature will go in a major version.
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected). Please, add the "breaking change" label to the PR. A migration guide must be created or updated.
[ ] This change requires a documentation update
[ ] Documentation fix/enhancement

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