Clean up of core module: part 1

[roosre]

addresses a few items of #670

• move example helpers to a separate namespace
• rename ACP to ACPInstance
• rename port_pyacp to port_acp
• rename image_name_pyacp to image_name_acp

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.

Project coverage is 94.32%. Comparing base (699324d) to head (37a5ef2).

Files with missing lines	Patch %	Lines
src/ansys/acp/core/extras/__init__.py	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #675 +/- ## ========================================== - Coverage 94.83% 94.32% -0.51% ========================================== Files 104 105 +1 Lines 5688 5690 +2 ========================================== - Hits 5394 5367 -27 - Misses 294 323 +29 ``` | [Flag](https://app.codecov.io/gh/ansys/pyacp/pull/675/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | Coverage Δ | | |---|---|---| | [python-3.10](https://app.codecov.io/gh/ansys/pyacp/pull/675/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | `94.11% <81.81%> (-0.51%)` | :arrow_down: | | [python-3.11](https://app.codecov.io/gh/ansys/pyacp/pull/675/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | `94.04% <81.81%> (-0.51%)` | :arrow_down: | | [python-3.12](https://app.codecov.io/gh/ansys/pyacp/pull/675/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | `94.25% <81.81%> (-0.51%)` | :arrow_down: | | [server-2024R2](https://app.codecov.io/gh/ansys/pyacp/pull/675/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | `90.77% <81.81%> (-0.51%)` | :arrow_down: | | [server-2025R1](https://app.codecov.io/gh/ansys/pyacp/pull/675/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | `94.04% <81.81%> (-0.51%)` | :arrow_down: | | [server-2025R2](https://app.codecov.io/gh/ansys/pyacp/pull/675/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | `94.04% <81.81%> (-0.51%)` | :arrow_down: | | [server-latest](https://app.codecov.io/gh/ansys/pyacp/pull/675/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | `94.11% <81.81%> (-0.51%)` | :arrow_down: | 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=ansys#carryforward-flags-in-the-pull-request-comment) to find out more.

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[greschd]

As a side note (maybe for a separate PR), we should also consider making the base pip install ansys-acp-core minimal. For example, PyVista could be optional.

This will require some changes to where dependencies are imported (maybe moving it to function-scope), and we will then need to test it also.