feat(iaas): onboard iaas project datasource

[marceljk]

Description

relates to #918 and STACKITTPR-300

Checklist

• Issue was linked above
• Code format was applied: make fmt
• Examples were added / adjusted (see examples/ directory)
• Docs are up-to-date: make generate-docs (will be checked by CI)
• Unit tests got implemented or updated
• Acceptance tests got implemented or updated (see e.g. here)
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)

[marceljk]

This is on hold because of some UnmarshalJSON issues in the IaaS service, where a enum has multiple matches in an oneOf schema. (See here)

This issue should be fixed, when stackitcloud/stackit-sdk-generator#182 is merged and the IaaS SDK is updated.

[github-actions]

Merging this branch will increase overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/stackitcloud/terraform-provider-stackit/stackit	1.92% (ø)
github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/iaas	0.00% (ø)
github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/iaas/project	46.15% (+46.15%)	🌟

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/iaas/project/datasource.go	46.15% (+46.15%)	65 (+65)	30 (+30)	35 (+35)	🌟
github.com/stackitcloud/terraform-provider-stackit/stackit/provider.go	1.92% (ø)	104	2	102

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/iaas/iaas_acc_test.go
• github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/iaas/project/datasource_test.go