When building thread_system as a submodule, the KCENON_HAS_COMMON_EXECUTOR
flag was not being defined, causing class layout mismatch between
thread_system and consuming projects like logger_system.

This resulted in Windows MSVC LNK2019 unresolved external symbol errors
for thread_pool::is_running() because the header declaration (with
override) and library implementation had different class layouts.

Changes:
- Add KCENON_HAS_COMMON_EXECUTOR=1 and KCENON_HAS_COMMON_RESULT=1
  definitions in core/CMakeLists.txt when executor_interface.h exists
- Ensures consistent class layout across all compilation units

Fixes: kcenon/logger_system#251

)

* feat: use KCENON feature detection for jthread and source_location

- Replace LOGGER_HAS_SOURCE_LOCATION with KCENON_HAS_SOURCE_LOCATION
- Replace LOGGER_HAS_JTHREAD with KCENON_HAS_JTHREAD
- Include kcenon/common/config/feature_flags.h for unified detection
- Keep LOGGER_HAS_* as legacy aliases for backward compatibility

Closes #250

* docs: update changelog for KCENON feature detection migration

* fix: remove override from deprecated log method for common_system v3.0.0 compatibility

The file/line/function overload of log() was removed from
common::interfaces::ILogger in common_system v3.0.0 (Issue #217).
This method is preserved for backward compatibility but no longer
overrides the interface method.

This fixes the build error:
  'log(...)' marked 'override', but does not override

* test: update ilogger_interface_test for common_system v3.0.0 API changes

The file/line/function overload of log() was removed from
ILogger interface in common_system v3.0.0 (Issue #217).

Update test to call the backward-compatible method directly on
logger class instead of through ILogger pointer.

* docs: update CHANGELOG for common_system v3.0.0 compatibility fix

Document the fix for the deprecated log method override issue
and test file update.

* ci: use thread_system feature branch for KCENON_HAS_COMMON_EXECUTOR fix

Update CI workflows to use thread_system feature branch that includes
the fix for KCENON_HAS_COMMON_EXECUTOR definition in submodule builds.

This resolves the Windows MSVC LNK2019 unresolved external symbol error
for thread_pool::is_running() that was caused by inconsistent class
layout between logger_system and thread_system builds.

Temporary change until thread_system PR is merged to main.

* ci: use UNIFIED_USE_LOCAL for local checkout dependencies

Enable UNIFIED_USE_LOCAL=ON in CI workflows to use locally checked out
common_system and thread_system instead of FetchContent downloading
from main branch.

This ensures that the thread_system feature branch with
KCENON_HAS_COMMON_EXECUTOR fix is used in the build.

* docs: update changelog with Windows MSVC linker fix

Document the fix for Windows MSVC LNK2019 unresolved external symbol
error for thread_pool::is_running().

Root cause: KCENON_HAS_COMMON_EXECUTOR was not defined when
thread_system was built as submodule, causing class layout mismatch.

Solution:
- thread_system core/CMakeLists.txt defines KCENON_HAS_COMMON_EXECUTOR=1
- CI workflows use UNIFIED_USE_LOCAL=ON for local dependencies