test: datasources name suggestions

[eliobischof]

• Tests singular datasource (Get requests) with example files
• Reuses configs created with dep instead of replacing substrings in examples
• Reduces logic for creating dependencies
• Contains changes from https://github.com/zitadel/terraform-provider-zitadel/pull/148

Definition of Ready

• [ ] Short description of the feature/issue is added in the pr description
• [ ] PR is linked to the corresponding user story
• [ ] Acceptance criteria are met
• [ ] All open todos and follow ups are defined in a new ticket and justified
• [ ] Deviations from the acceptance criteria and design are agreed with the PO and documented.
• [ ] No debug or dead code
• [ ] My code has no repetitions
• [ ] All non-functional requirements are met
• [ ] The generic lifecycle acceptance test passes for affected resources.
• [ ] Examples are up-to-date and meaningful. The provider version is incremented.
• [ ] Docs are generated.
• [ ] Code is generated where possible.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (2ea7370) 63.20% compared to head (d3f9249) 63.20%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## datasources-name #149 +/- ## ================================================= Coverage 63.20% 63.20% ================================================= Files 156 156 Lines 12609 12609 ================================================= Hits 7969 7969 Misses 3379 3379 Partials 1261 1261 ``` | [Flag](https://app.codecov.io/gh/zitadel/terraform-provider-zitadel/pull/149/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zitadel) | Coverage Δ | | |---|---|---| | [acceptance-tests](https://app.codecov.io/gh/zitadel/terraform-provider-zitadel/pull/149/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zitadel) | `63.20% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zitadel#carryforward-flags-in-the-pull-request-comment) to find out more.

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