modbus: add 64-bit byte order support for WS and WR

[moruoxian]

Summary

Add support for WS (34 12 78 56) and WR (56 78 12 34) as additional 64-bit byte orders for Modbus int64, uint64, and double tags.

This change extends address suffix parsing, updates 64-bit endian conversion in the Modbus read/write paths, updates the Modbus TCP/RTU schemas, and adds functional test coverage.

Validation

• cherry-picked cleanly onto current upstream/main
• Python functional test file syntax checked successfully
• local full CMake validation was blocked by missing librdkafka in the current environment, unrelated to this Modbus change

[codecov-commenter]

Codecov Report

❌ Patch coverage is 67.01031% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.05%. Comparing base (207da6d) to head (c99999b).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
plugins/modbus/modbus_req.c	42.85%	20 Missing ⚠️
src/adapter/driver/driver.c	50.00%	12 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2736   +/-   ##
=======================================
  Coverage   65.04%   65.05%           
=======================================
  Files         129      129           
  Lines       31290    31387   +97     
=======================================
+ Hits        20353    20419   +66     
- Misses      10937    10968   +31     

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