test: add some unit tests for the property to string functions
test: add some unit tests for the property to string functions

That is: ossl_property_name_str and ossl_property_value_str.

These only have high level tests during the creation of child library
contexts.

Reviewed-by: Tomas Mraz <2bc6038c3dfca09b2da23c8b6da8ba884dc2dcc2@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17325)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl