redfish-core: Refactor getManagedHostProperty

The getManagedHostProperty function contained an inline lambda that
triggered the long-lambda ast-grep rule, requiring an inline
suppression (// ast-grep-ignore: long-lambda).

This commit extracts the lambda into a separate
afterGetManagedHostProperty function and uses std::bind_front to
handle the asynchronous callback. This aligns the code with the
preferred bmcweb pattern for D-Bus callbacks, improves readability,
and allows the removal of the static analysis suppression.

Tested:
- No other functional change.
- Tested on an AST2600 SoC platform.
- Redfish Service Validator passed with no new errors or warnings
introduced.

Change-Id: I8e1fe0aae26b07a4f84c1d41aef536627f7051ac
Signed-off-by: Yuvakumar Selvamani <yuvakumars@ami.com>