Add Mbed TLS 4.x support (PSA Crypto) for macOS

Auto-detect Mbed TLS 4.x via MBEDTLS_VERSION_MAJOR and adapt the backend:
- Include psa/crypto.h and drop the headers removed in 4.x (ctr_drbg,
  entropy, md5, sha*), gated behind the version macro.
- Compute MD5/SHA-256/SHA-512 via PSA (psa_hash_compute) and initialize
  PSA Crypto once with std::call_once.
- Drop the explicit entropy/CTR-DRBG RNG (PSA provides the TLS RNG) and
  skip the RNG-callback overloads of pk_parse_key/pk_check_pair on 4.x.
- Retry on a TLS 1.3 NewSessionTicket (the 4.x default) in connect, read,
  write and is_peer_closed via a single mbedtls_is_session_ticket() helper,
  so online HTTPS works, including large redirected downloads where the
  ticket arrives mid-write.

Note V4 implies V3, so 3.x-only paths now check V3 && !V4.

Build systems (macOS): the CMake config and pkg-config shipped by Homebrew
resolve 4.x transitively, so CMakeLists.txt and meson.build need no change
for linking; the Makefile links libtfpsacrypto when present, else
libmbedcrypto.

Tests: generate the encrypted client key as both PBES2-AES (3.6+/4.x,
OpenSSL, wolfSSL) and PBES1-3DES (Mbed TLS 2.28) and pick by version, since
4.x dropped DES and 2.28 lacks PBES2. Also generate the IP-host certs in
test/meson.build to match gen-certs.sh and CMakeLists.txt.

test/Makefile

@@ -9,7 +9,9 @@ ifneq ($(OS), Windows_NT)
 		OPENSSL_SUPPORT = -DCPPHTTPLIB_OPENSSL_SUPPORT -I$(OPENSSL_DIR)/include -L$(OPENSSL_DIR)/lib -lssl -lcrypto
 		OPENSSL_SUPPORT += -framework CoreFoundation -framework Security
 		MBEDTLS_DIR ?= $(shell brew --prefix mbedtls@3)
-		MBEDTLS_SUPPORT = -DCPPHTTPLIB_MBEDTLS_SUPPORT -I$(MBEDTLS_DIR)/include -L$(MBEDTLS_DIR)/lib -lmbedtls -lmbedx509 -lmbedcrypto
+		# Mbed TLS 4.x renamed libmbedcrypto to libtfpsacrypto; pick whichever exists.
+		MBEDTLS_CRYPTO_LIB ?= $(shell test -f "$(MBEDTLS_DIR)/lib/libtfpsacrypto.dylib" -o -f "$(MBEDTLS_DIR)/lib/libtfpsacrypto.a" && echo tfpsacrypto || echo mbedcrypto)
+		MBEDTLS_SUPPORT = -DCPPHTTPLIB_MBEDTLS_SUPPORT -I$(MBEDTLS_DIR)/include -L$(MBEDTLS_DIR)/lib -lmbedtls -lmbedx509 -l$(MBEDTLS_CRYPTO_LIB)
 		MBEDTLS_SUPPORT += -framework CoreFoundation -framework Security
 		WOLFSSL_DIR ?= $(shell brew --prefix wolfssl)
 		WOLFSSL_SUPPORT = -DCPPHTTPLIB_WOLFSSL_SUPPORT -I$(WOLFSSL_DIR)/include -I$(WOLFSSL_DIR)/include/wolfssl -L$(WOLFSSL_DIR)/lib -lwolfssl