Params conversion tests.

Add ranged checked OSSL_PARAM conversions between the native types.  A
conversion is legal only if the given value can be exactly represented
by the target type.

Includes a test case that reads a stanza test case file and verified that param
conversions are processed properly.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8733)