[feature][services] add thread-safe STSAFE guard for session-scoped a…

[Grom-]

…nd per-transfer access

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[parmi93]

In our platform I added a same thread-safe guard in the I2C PAL functions, where a FreeRTOS mutex is locked in stse_platform_i2c_send_start()/stse_platform_i2c_receive_start() and unlocked in stse_platform_i2c_send_stop()/stse_platform_i2c_receive_stop(). The mutex can be unlocked in stse_platform_i2c_send_continue()/stse_platform_i2c_receive_continue() as well in case of an error (e.g. STSE_PLATFORM_BUFFER_ERR).

So I think this guard mechanism should be extended for non-Linux platform as well, maybe through some new PAL guard functions.

[Grom-]

@parmi93 , yes , good point , I will extend it to non-Linux platform