Make SHA-3 required with OpenSSL

[vcsjones]

This is an alternative to #120989.

This makes SHA-3 required for OpenSSL, effectively making our OpenSSL minimum 1.1.1.

[Copilot]

Pull Request Overview

This PR makes SHA-3 support required when using OpenSSL, effectively establishing OpenSSL 1.1.1 as the minimum supported version. Previously, SHA-3 was treated as an optional "light-up" feature that was conditionally available.

Key changes:

• Removes conditional compilation and runtime checks for SHA-3 availability
• Simplifies code by treating SHA-3 algorithms (SHA3-256, SHA3-384, SHA3-512, SHAKE128, SHAKE256) as always available
• Converts SHA-3 functions from LIGHTUP_FUNCTION to REQUIRED_FUNCTION in the OpenSSL shim layer

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pal_evp.c	Removes BUILD_MD_FETCH_LIGHTUP_SHA3 macro and conditional SHA-3 support; converts SHA-3 digest functions to use standard BUILD_MD_FETCH macro
pal_crypto_config.h.in	Removes HAVE_OPENSSL_SHA3 configuration option
opensslshim.h	Removes SHA-3 function declarations for older OpenSSL versions; changes SHA-3 functions from LIGHTUP to REQUIRED
configure.cmake	Removes CMake check for EVP_sha3_256 function existence
Interop.EVP.DigestAlgs.cs	Simplifies SHA-3 caching logic and removes platform availability checks; converts switch to switch expression

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-security, @bartonjs, @vcsjones
See info in area-owners.md if you want to be subscribed.

[vcsjones]

n.b. there is still a lot of cleanup that can be done if we remove all of the 1.1.0 and 1.0.x compatibility. However this PR is partially serving to gauge appetite for this change before I invest too much in cleanup.