Fix ov::Any string conversion for windows

[rasapala]

Details:

Fix unsafe type conversion in CPU plugin property handling

Fixes a potential crash caused by forcing numeric ov::Any values to
std::string through iostream conversion, which is unstable on Windows.

The CPU plugin's Config::readProperties unconditionally converts incoming
plugin properties to std::string before parsing, triggering unsafe iostream
type conversions when clients pass numeric types (int64_t, int) for
NUM_STREAMS or similar numeric properties.

This causes:

• Unsafe iostream-based conversion path in ov::Any.asstd::string()
• Possible memory corruption or segfault on Windows
• Crashes in openvinotoolkit/openvino#XXXXX

Fix: Check the actual ov::Any type before conversion. Use native casts
for numeric types (int64_t, int) and only use iostream conversion path
for true string values.

Safe path is: numeric input -> std::to_string -> string -> parse
Unsafe path was: numeric input -> iostream conversion -> corrupted string -> crash

Fixes clients that pass:

• {"NUM_STREAMS": 4} as ov::Any(int64_t(4))
• {"NUM_STREAMS": 4} as ov::Any(int(4))
• {"num_requests": 8} as ov::Any(int64_t(8))

Changes:

• ov::num_streams handling: type-aware conversion
• ov::hint::num_requests handling: type-aware conversion

Tickets:

• None

AI Assistance:

• *AI assistance used: yes
• *AI was used to search for a possible problem during OVMS sporadic unit test failure and propose solution.
• Unit tests and root cause fixed and added here: Fix plugin config sporadic and fix proxy test model_server#4188