Adjustments for OpenSSL 3.0.0

[tomuben]

Background

In OpenSSL 3.0.0 several functions which are used in r-exasol are declared as deprecated:

FAILED: CMakeFiles/r_exasol_tests.dir/home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp.o 
  /usr/bin/c++  -I/home/runner/work/r-exasol/r-exasol/tests/cpp/../../src -I/usr/share/R/include -I/home/runner/work/r-exasol/b/_deps/catch-src/single_include -g -fno-omit-frame-pointer -fsanitize=address -Wall -Wextra -pedantic -Werror -Wno-deprecated -std=gnu++14 -MD -MT CMakeFiles/r_exasol_tests.dir/home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp.o -MF CMakeFiles/r_exasol_tests.dir/home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp.o.d -o CMakeFiles/r_exasol_tests.dir/home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp.o -c /home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp
  /home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp: In member function ‘void exa::ssl::Certificate::mkcert(int, int, int)’:
  Error: /home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp:97:18: error: ‘RSA* RSA_new()’ is deprecated: Since OpenSSL 3.0 [-Werror=deprecated-declarations]
     97 |     rsa = RSA_new();
        |           ~~~~~~~^~
  In file included from /usr/include/openssl/x509.h:36,
                   from /home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.h:4,
                   from /home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp:2:
  /usr/include/openssl/rsa.h:201:28: note: declared here
    201 | OSSL_DEPRECATEDIN_3_0 RSA *RSA_new(void);
        |                            ^~~~~~~
  Error: /home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp:102:34: error: ‘int RSA_generate_key_ex(RSA*, int, BIGNUM*, BN_GENCB*)’ is deprecated: Since OpenSSL 3.0 [-Werror=deprecated-declarations]
    102 |     int ret = RSA_generate_key_ex(rsa, bits, bn, nullptr);
        |               ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
  In file included from /usr/include/openssl/x509.h:36,
                   from /home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.h:4,
                   from /home/runner/work/r-exasol/r-exasol/src/r_exasol/ssl/certificate.cpp:2:
  /usr/include/openssl/rsa.h:2[60](https://github.com/exasol/r-exasol/actions/runs/3759303716/jobs/6388707194#step:7:62):27: note: declared here
    260 | OSSL_DEPRECATEDIN_3_0 int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e,
        |                           ^~~~~~~~~~~~~~~~~~~
  cc1plus: all warnings being treated as errors

The OpenSSL 3.0.0 migration guide claims:

Deprecated low-level object creation

Low-level objects were created using methods such as RSA_new(3), RSA_up_ref(3) and RSA_free(3). Applications should instead use the high-level EVP_PKEY APIs, e.g. EVP_PKEY_new(3), EVP_PKEY_up_ref(3) and EVP_PKEY_free(3). See also EVP_PKEY_CTX_new_from_name(3) and EVP_PKEY_CTX_new_from_pkey(3).

EVP_PKEYs may be created in a variety of ways: See also "Deprecated low-level key generation functions", "Deprecated low-level key reading and writing functions" and "Deprecated low-level key parameter setters".

Acceptance Criteria

1. Adjust to new OpenSSL interface (using high level key generation functions)
2. Treat all warnings as errors again here