Prevent hidden use of non-IRAM interrupt service routines via FunctionalInterrupt API

[dok-net]

If one uses the FunctionaInterrupt attachInterrupt, the ESP32 will accept and execute ISRs that are not in IRAM. The C++ compiler currently does not (same problem in ESP8266) honor IRAM_ATTR for std::bind, std::function, or lambdas - probably never will, or otherwise a lot of std-namespace code would have to be marked as IRAM_ATTR.
This problem is avoided by either either removing (#2734 ) the problematic FunctionalInterrupt interface, or by providing safe scheduling for std::function, std::bind, lambdas through "scheduled ISRs." (TBD, under investigation )

[dok-net]

#1344 btw is not thread-safe AFAIK.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This stale issue has been automatically closed. Thank you for your contributions.

[fimtrey]

This may save some people some time. @dok-net Thank you for the clarification.