ext/openssl: allow constructing a public-only RSA key

[JanTvrdik]

Resolves #22702

[Copilot]

Pull request overview

This PR updates the OpenSSL extension so openssl_pkey_new() can construct an RSA public-only key from raw parameters (n and e), aligning RSA behavior with the existing public-key construction support for DSA/DH/EC and enabling clean public-key verification flows (e.g., WebAuthn/COSE RSA keys).

Changes:

• Allow RSA key construction without providing the private exponent d, and propagate an is_private flag into the OpenSSLAsymmetricKey wrapper.
• Update the OpenSSL 1.x and 3.x backends to select public-key vs keypair construction appropriately.
• Add a PHPT test covering reconstruction from n/e and verifying/encrypting with the resulting key; document the change in UPGRADING.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
UPGRADING	Documents the new RSA public-only construction behavior for openssl_pkey_new().
ext/openssl/tests/openssl_pkey_new_rsa_public.phpt	Adds regression coverage for constructing an RSA public key from n/e and using it in verify/encrypt flows.
ext/openssl/php_openssl_backend.h	Updates the RSA init function signature to return an is_private out-param.
ext/openssl/openssl.c	Uses the new is_private out-param when wrapping RSA keys from openssl_pkey_new().
ext/openssl/openssl_backend_v3.c	Implements RSA public-only creation via OpenSSL 3 fromdata() selection (PUBLIC_KEY vs KEYPAIR).
ext/openssl/openssl_backend_v1.c	Implements RSA public-only creation in the legacy backend and threads is_private through the init path.

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