Add a software crypto-callback device (wc_swdev) that lets the wolfcrypt
test suite run under WOLF_CRYPTO_CB_ONLY_* flags without per-test devId
plumbing. The bundle is a separately-compiled second copy of wolfcrypt
(software implementations enabled, WOLF_CRYPTO_CB_ONLY_* stripped) linked
into testwolfcrypt as a single relocatable object; every symbol is demoted
to local via objcopy --keep-global-symbol except wc_SwDev_Callback, so there
is no collision with the main libwolfssl.
A find callback routes unbound operations (devId == INVALID_DEVID) to the
swdev while letting real device IDs pass through.
wc_SwDev_Init / wc_SwDev_Cleanup hooks are wired into wolfcrypt/test/test.c.
cryptocb_test's WOLF_CRYPTO_CB_FIND and WOLF_CRYPTO_CB_ONLY_RSA blocks are
gated off under WOLFSSL_SWDEV.
Enable via --enable-swdev (requires --enable-cryptocb).
rizlik