Add Timestamp support to CAN Testlib
Add support for reading timestamp into CANTest lib.
In: test/lib/CANTestlib.vhd add function: CAN_read_timestamp.
This function will read from TIMESTAMP_LOW_ADR and TIMESTAMP_HIGH_ADR, concatenate the values to one std_logic_vector, and return this vector (as a variable assignment). Since VHDL does not have 64 bit int type, returning as std_logic_vector(63 downto 0) is enough. Also in SW_CAN_Frame_type this is used as timestamp reference.
Also, add proper function header with comments and argument explanation as in the other functions.
This function will be then used by timestamp test.