add regular scheduled functions, now also callable on yield() (#6039)

* add regular scheduled functions, now also callable on `yield()`

added bool schedule_function_us(std::function<bool(void)> fn, uint32_t repeat_us)
lambda must return true to be not removed from the schedule function list
if repeat_us is 0, then the function is called only once.

Legacy schedule_function() is preserved

This addition allows network drivers like ethernet chips on lwIP to be regularly called
- even if some user code loops on receiving data without getting out from main loop
  (callable from yield())
- without the need to call the driver handling function
  (transparent)

This may be also applicable with common libraries (mDNS, Webserver, )

tests/host/common/mock.h

@@ -131,8 +131,6 @@ void mockUDPSwallow (size_t copied, char* ccinbuf, size_t& ccinbufsize);
 class UdpContext;
 void register_udp (int sock, UdpContext* udp = nullptr);
 
-class InterruptLock { };
-
 //
 
 void mock_start_spiffs (const String& fname, size_t size_kb, size_t block_kb = 8, size_t page_b = 512);