tinycrypt: deprecate the library

Since we now have PSA Crypto APIs/Mbed TLS alternatives for crypto
operations in all Zephyr's codebase we can start the deprecation
of the TinyCrypt libary (as planned from #43712).
This commit is only the inital step: updates documentation and
add the DEPRECATED Kconfig option to the TINYCRYPT one.

Signed-off-by: Valerio Setti <vsetti@baylibre.com>