tests: net: sockets: tcp: add a tls tests

[cfriedt]

Is your enhancement proposal related to a problem? Please describe.
Currently I'm attempting to use mbedTLS in a custom application and am creating a test to verify TLS in CI. The test is multi-threaded and uses TCP sockets with the TLS extensions; the server server socket is managed by one thread and the client socket is managed by the main thread.

My reference(s) for the application were the echo_server / echo_client sample applications and I'm just using the certificates / keys from those sample applications as-is. However, I'm experiencing a handshake error in TLS.

Describe the solution you'd like
It might be useful to have it a test that verified this kind of functionality in Zephyr CI

Describe alternatives you've considered
Have looked around for existing tests that exercise this particular setup, but have found none.

Additional context
Current handshake error:

*** Booting Zephyr OS build zephyr-v2.4.0-2547-gb68f47fdb9a0  ***
W: No entropy device on the system, TLS communication may be insecure!
I: Initializing network
I: Initializing built-in certificates
D: Adding CA Certificate (783 bytes)
D: Adding Server Certificate (Public Key) (693 bytes)
D: Adding Server Certificate (Private Key) (1219 bytes)
...
D: (main): Allocated TLS context, 0x2000189c
D: (main): socket: ctx=0x20005840, fd=1
I: CPort 0 mapped to TCP/IP port 4242
D: (main): Allocated TLS context, 0x20001c74
D: (main): socket: ctx=0x200058c8, fd=3
I: CPort 1 mapped to TCP/IP port 4243
...
D: (main): Allocated TLS context, 0x2000204c
D: (main): socket: ctx=0x20005950, fd=5
D: (rx_q[0]): parent=0x200058c8, ctx=0x200059d8, st=0
D: (main): there are 1 tags
D: (main): tag[0]: 0
D: (main): found tag
E: returning tls_add_ca_certificate()
E: calling mbedtls_x509_crt_parse(0x200021b4, 0x2e047, 783)
D: (main): found a CA cert
D: (rx_q[0]): ctx=0x200059d8, pkt=0x2000ba60, st=0, user_data=(nil)
D: (greybus): accept: ctx=0x200059d8, fd=7
D: (greybus): Allocated TLS context, 0x20002424
D: (greybus): there are 1 tags
D: (greybus): tag[0]: 1
D: (greybus): found tag
E: returning tls_set_own_cert()
E: tls_set_credential() failed (-22)
E: tls_mbedtls_set_credentials() failed (-22)
E: tls_mbedtls_init() failed (-22)
D: (greybus): close: ctx=0x200059d8, fd=7
D: (greybus): discarding pkt 0x2000ba60
D: (rx_q[0]): ctx=0x20005950, pkt=(nil), st=-104, user_data=(nil)
D: (rx_q[0]): Marked socket 0x20005950 as peer-closed
D: (main): NULL return from fifo
E: TLS handshake error: -7280
ASSERTION FAIL [r == 0] @ CMAKE_SOURCE_DIR/src/gpio.c:147
	connect: 113
E: r0/a1:  0x00000004  r1/a2:  0x00000093  r2/a3:  0x90000000
E: r3/a4:  0x0002880b r12/ip:  0x00000000 r14/lr:  0x00000c6f
E:  xpsr:  0x41000000
E: Faulting instruction address (r15/pc): 0x0001ca2a
E: >>> ZEPHYR FATAL ERROR 4: Kernel panic on CPU 0
E: Current thread: 0x20001300 (main)
E: Halting system
qemu-system-arm: terminating on signal 2
ninja: build stopped: interrupted by user.

[jukkar]

How this is different from #30936, do we need two TLS issues that look identical?

[cfriedt]

Looks line I made a duplicate issue.