test: use runtime FIPS detection instead of compile-time check

test: use runtime FIPS detection instead of compile-time check

Replace #ifdef FIPS_MODULE with OSSL_PROVIDER_available() runtime check
in ecdsatest.c. The compile-time check is not meaningful for test cases
as the test binary may be compiled without FIPS_MODULE but run with the
FIPS provider loaded.

Fixes #28255

CLA: trivial

Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/29527)