Add configuration define to disable br_sslio_close

[pennam]

From BearSSL docs:

br_sslio_close(): perform the SSL closure protocol. This entails sending a close_notify alert, and receiving a close_notify response.

Note that a number of deployed SSL implementations do not follow the protocol for closure, and may drop the underlying socket abruptly. As such, errors are often reported by br_sslio_close().

In case of mbed-os + ArduinoIoTCloud br_sslio_close is endless looping blocking sketch execution.

[github-actions]

Memory usage change @ 32e43bb

Board	flash	%	RAM for global variables	%
arduino:mbed_giga:giga	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_nano:nanorp2040connect	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_opta:opta	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A
arduino:megaavr:uno2018	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkr1000	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrgsm1400	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrnb1500	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board	examples/SHA1 flash	%	examples/SHA1 RAM for global variables	%	examples/SHA256 flash	%	examples/SHA256 RAM for global variables	%	examples/WiFiSSLClient flash	%	examples/WiFiSSLClient RAM for global variables	%	examples/MKRGSMSSLClient flash	%	examples/MKRGSMSSLClient RAM for global variables	%
arduino:mbed_giga:giga	0	0.0	0	0.0	0	0.0	0	0.0
arduino:mbed_nano:nanorp2040connect	0	0.0	0	0.0	0	0.0	0	0.0
arduino:mbed_opta:opta	0	0.0	0	0.0	0	0.0	0	0.0
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
arduino:megaavr:uno2018	0	0.0	0	0.0	0	0.0	0	0.0
arduino:samd:mkr1000	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0
arduino:samd:mkrgsm1400	0	0.0	0	0.0	0	0.0	0	0.0					0	0.0	0	0.0
arduino:samd:mkrnb1500	0	0.0	0	0.0	0	0.0	0	0.0

Click for full report CSV

Board,examples/SHA1<br>flash,%,examples/SHA1<br>RAM for global variables,%,examples/SHA256<br>flash,%,examples/SHA256<br>RAM for global variables,%,examples/WiFiSSLClient<br>flash,%,examples/WiFiSSLClient<br>RAM for global variables,%,examples/MKRGSMSSLClient<br>flash,%,examples/MKRGSMSSLClient<br>RAM for global variables,%
arduino:mbed_giga:giga,0,0.0,0,0.0,0,0.0,0,0.0
arduino:mbed_nano:nanorp2040connect,0,0.0,0,0.0,0,0.0,0,0.0
arduino:mbed_opta:opta,0,0.0,0,0.0,0,0.0,0,0.0
arduino:mbed_portenta:envie_m7,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A
arduino:megaavr:uno2018,0,0.0,0,0.0,0,0.0,0,0.0
arduino:samd:mkr1000,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0
arduino:samd:mkrgsm1400,0,0.0,0,0.0,0,0.0,0,0.0,,,,,0,0.0,0,0.0
arduino:samd:mkrnb1500,0,0.0,0,0.0,0,0.0,0,0.0,,,,,,,,