Data Source: oxide_vpcs

[sudomateo]

Summary

• add the oxide_vpcs data source for listing every VPC in a project by project name or ID
• expose VPC identity, networking, project, router, and timestamp fields
• register the data source and add generated documentation, an example, and a changelog entry

Linear: SSE-298

Tests

• make test (224 tests passed; 147 acceptance tests skipped without TF_ACC)
• make lint
• make test TEST_PACKAGE=./internal/provider/vpcs TEST_NAME='TestDataSourceVPCs$'

Test limitation

• make testacc-sim could not start because this orb has neither a Docker daemon nor the Docker Compose plugin. The added acceptance test is included but could not be executed locally.