Move BearSSL from STACK_PROXY to a real, thunked 2nd stack (#5168)

* Update to BearSSL 0.6+ release, add AES_CCM modes

Pull in latest BearSSL head (0.6 + minor additions) release and add AES_CCM
modes to the encryption options.

* Enable the aes_ccm initialization in client/server

* Initial attempt

* Working code with second stack thunking

* Remove #ifdefs in .S file, not needed.

* Clean up thunks and remove separate stack flag

* Fix PIO assembler errors

* Remove #ifdef code changes, ensure same code as PC

Remove "#ifdef ESP8266;...;#else;...;#endif" brackets in BearSSL to
ensure the host-tested code is the same as the ESP8266-run code.

* Move to latest BearSSL w/EC progmem savings

* Merge with master

* Add br_thunk_* calls to do ref counting, painting

Add reference counting br_thunk_add/del_ref() to replace stack handling code
in the class.

Add in stack painting and max usage calculation.

* Add in postmortem stack dump hooks

When a crash occurs while in the second stack, dump the BSSL stack and
then also the stack that it was called from (either cont or sys).

* Update stack dump to match decoder expectations

* Move thunk to code core for linkiage

The thunk code needs to be visible to the core routines, so move it to the
cores/esp8266 directory.  Probably need to refactor the stack setup and the
bearssl portion to avoid dependency on bearssl libs in cores/esp8266

* Add 2nd stack dump utility routine

* Refactor once more, update stack size, add stress

Make stack_thunks generic, remove bearssl include inside of cores/esp8266.

Allocate the stack on a WiFiServerSecure object creation to avoid
fragmentation since we will need to allocate the stack to do any
connected work, anyway.

A stress test is now included which checks the total BearSSL second
stack usage for a variety of TLS handshake and certificate options
from badssl.org.

* Update to latest to-thunks branch

* Add BearSSL device test using stack stress

Run a series of SSL connection and transmission tests that stress
BearSSL and its stack usage to the device tests.

Modify device tests to include a possible SPIFFS generation and
upload when a make_spiffs.py file is present in a test directory.

* Use bearssl/master branch, not /to-thunks branch

Update to use the merged master branch of bearssl.  Should have no code
changes.

tools/sdk/include/bearssl/bearssl.h

@@ -136,7 +136,6 @@
 #include "bearssl_ssl.h"
 #include "bearssl_x509.h"
 #include "bearssl_pem.h"
-#include "bearssl_port.h"
 
 /** \brief Type for a configuration option.
  *

tools/sdk/include/bearssl/bearssl_git.h

@@ -1,2 +1,2 @@
 // Do not edit -- Automatically generated by tools/sdk/ssl/bearssl/Makefile
-#define BEARSSL_GIT f55a6ad
+#define BEARSSL_GIT 0e71e46