Silence bogus MSVC warning C4232. Use the method already used
for similar cases earlier.
Also fixup existing suppressions to use pragma push/pop.
```
lib\vquic\curl_ngtcp2.c(709,40): error C2220: the following warning is treated as an error
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'client_initial': address of dllimport 'ngtcp2_crypto_client_initial_cb' is not static, identity not guaranteed
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'recv_crypto_data': address of dllimport 'ngtcp2_crypto_recv_crypto_data_cb' is not static, identity not guaran
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'encrypt': address of dllimport 'ngtcp2_crypto_encrypt_cb' is not static, identity not guaranteed
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'decrypt': address of dllimport 'ngtcp2_crypto_decrypt_cb' is not static, identity not guaranteed
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'hp_mask': address of dllimport 'ngtcp2_crypto_hp_mask_cb' is not static, identity not guaranteed
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'recv_retry': address of dllimport 'ngtcp2_crypto_recv_retry_cb' is not static, identity not guaranteed
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'update_key': address of dllimport 'ngtcp2_crypto_update_key_cb' is not static, identity not guaranteed
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'delete_crypto_aead_ctx': address of dllimport 'ngtcp2_crypto_delete_crypto_aead_ctx_cb' is not static, identit
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'delete_crypto_cipher_ctx': address of dllimport 'ngtcp2_crypto_delete_crypto_cipher_ctx_cb' is not static, ide
lib\vquic\curl_ngtcp2.c(709,40): warning C4232: nonstandard extension used: 'get_path_challenge_data': address of dllimport 'ngtcp2_crypto_get_path_challenge_data_cb' is not static, ident
```
Ref: https://github.com/curl/curl/actions/runs/10343459009/job/28627621355#step:10:30
Cherry-picked from #14495
Co-authored-by: Tal Regev
Ref: #14383Closes#14510
457427e03f