[DOCS] Update S7 & OPC UA documentation and fix protocol compatibility matrix

[klaus321901]

What does this PR do?

This PR updates outdated and incomplete documentation for S7 and OPC UA protocols, refreshes the compatibility matrix, and fixes a broken link in the IoTDB integration guide.

Changes made

• S7 Documentation (s7.adoc)

  • Replaced placeholder TODO entries with meaningful descriptions for counters, timers, and memory areas.
  • Clarified compatibility across Siemens S7-300/400, S7-1200/1500, and LOGO devices.

• OPC UA Documentation (opcua.adoc)

  • Added details on secure communication, certificate handling, and negotiation procedures.
  • Updated tested compatibility list with specific server versions.

• Protocols Index (index.adoc)

  • Fixed outdated protocol support indicators in the compatibility matrix.

  • Corrected inconsistencies between language support and actual driver capabilities.

  • IoTDB Integration (apache-iotdb.adoc)
    -Fixed broken example link that previously pointed to a non-existent path.
    -Updated integration guide to correctly reference plc4x-extras repository.

Issues Fixed

• Why is this important?

• Fixes [DOCUMENTATION]: Inaccurate PLC Protocol Compatibility Matrix Webpage - Update Needed! #2023 (Inaccurate PLC protocol compatibility documentation
• Fixes [DOCUMENTATION]: IoTDB documentation refers to missing example #2019 (IoTDB documentation refers to missing example).

Why is this important?

• Outdated compatibility info can confuse users and deter contributors.
• This PR addresses Issue #2023.
• Broken IoTDB documentation link prevented users from finding a working integration example.

Notes

• Verified changes against official Siemens and OPC UA documentation.
• Cross-checked with existing PLC4X functionality and recent release notes.

[klaus321901]

This PR also fixes Issue #2019 by correcting the IoTDB integration example link.

[ottlukas]

Unfortunately this PR can not be accepted as it seems to be AI generated updating of documenation, without further explaination, nor understanding of the S7 protocol. Can you further elaborate? And may bring some of the detailed explaination to the mailing list as well? Thank you! In the age of agentic AI a lot of changes are often not adding a lot of additinal value in projects like ours. As there is not much public data available for the LLMs to pick up (at least this my impression after experimenting with Jules, Github Copilot)

[klaus321901]

Thanks for the feedback, I really appreciate it. To be transparent: I did use an AI tool to help with drafting some of the wording, but I recognize that was not enough. I should have provided proper references to the Siemens S7 manuals and the PLC4X code to show why the edits are correct.

I’ll revisit this with clearer explanations and source references, and if needed, I’ll also bring it to the mailing list for broader discussion. For now, I’ll pause this PR and come back with something more solid.