VCS and Verilator support

[LucaRufer]

Minimal changes required to compile sources and simulation targets for VCS (version W-2024.09-1) and Verilator (v5.028-44-g1d79f5c59):

• Verilator requires the std:: prefix when using built-in classes like std::semaphore and std::mailbox.
• Verilator cannot compute static variables at compile time when conditional operator is used.
• Verilator cannot determine the default type for Associative Arrays if a parameter is used.
• VCS requires parameter types to match when calling a function with a class object. If any of the axi_??_beat classes are instantiated directly and not from the typedefs in axi_driver, they cannot be passed to a function of a axi_driver object, as parameter and parameter int are not the same.