[php-src] PR #24060: Fix GH-20175: CertificateGenerator falls back to 1024-bit keys

Pull Request: https://github.com/php/php-src/pull/24060 Author: bukka CertificateGenerator::generateKey() called openssl_pkey_new() without the test config, so it depended on the system openssl.cnf. When that file is missing, openssl_pkey_new() silently returns false and openssl_csr_new() generates the key itself using default_bits from the supplied config, which was 1024. OpenSSL 3.2+ defaults to security level 2 which rejects such keys, so TLS tests like gh10495 fail. Pass the test config explicitly so the explicit private_key_bits always applies, and bump the inline default_bits to 2048 for consistency. Closes GH-20176.