md4, md5: switch to wolfCrypt API in wolfSSL builds

[vszakats]

Replacing the OpenSSL-like compatibility interface, and syncing with other
hashes, when building with wolfSSL.

Also: stop stomping on OpenSSL public MD4 symbols. This makes the wolfSSL
coexist workaround unnecessary, while also syncing up with MD5 sources.

After this patch the only remaining reference to wolfSSL's OpenSSL
compatibility layer is in lib/curl_ntlm_core.c.

[Copilot]

Pull request overview

This PR updates curl’s MD4/MD5 implementations for wolfSSL builds to use the native wolfCrypt API instead of the OpenSSL-compatibility layer, aligning behavior with other wolfCrypt-backed hashes in the codebase.

Changes:

• MD5: remove wolfSSL OpenSSL-compat header usage and switch to <wolfssl/wolfcrypt/md5.h> + wc_* APIs.
• MD4: switch wolfSSL implementation to <wolfssl/wolfcrypt/md4.h> and add thin wrappers matching the existing MD4_Init/Update/Final call pattern.

Reviewed changes

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

File	Description
lib/md5.c	Switch wolfSSL MD5 backend from OpenSSL-compat API to wolfCrypt wc_Md5 APIs.
lib/md4.c	Switch wolfSSL MD4 backend to wolfCrypt and wrap wc_* calls behind MD4_Init/Update/Final.

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