Rename SecurityTransforms to AppleCrypto

[vcsjones]

Our internal implementations of algorithms for the Apple platform are called "SecurityTransforms" despite not having used SecurityTransforms since around .NET 5 (DSA withstanding, but that was removed). Apple doesn't really give a distinct name to their in-house cryptography library (CryptoKit aside), opting to just call it "Security", to or possibly "Key Services".

Let's rename them to just "AppleCrypto" to avoid the misdirection to anyone new to the code base.

[Copilot]

Pull Request Overview

This PR renames the Apple platform cryptographic implementations from "SecurityTransforms" to "AppleCrypto" to better reflect their actual implementation. The change addresses the misleading name since these implementations haven't used Apple's SecurityTransforms framework since around .NET 5, instead relying on Apple's core Security framework.

Key Changes:

• Rename all class names from *SecurityTransforms to *AppleCrypto
• Update file names from *SecurityTransforms.* to *AppleCrypto.*
• Update project file references to use the new file names

Reviewed Changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
X509Pal.macOS.cs	Updated RSA class instantiation to use new AppleCrypto naming
X509Pal.iOS.cs	Updated RSA class instantiation to use new AppleCrypto naming
X509Pal.Apple.ECKey.cs	Updated ECDsa and ECDiffieHellman class instantiations
X509CertificateLoader.macOS.cs	Updated key creation and type checking for new class names
X509CertificateLoader.iOS.cs	Updated key creation for new class names
AppleCertificatePal.cs	Updated private key method returns to use new class names
AppleCertificatePal.Keys.macOS.cs	Updated type casting for private key operations
RSACryptoServiceProvider.Unix.cs	Updated comment to reflect new naming
RSA.Create.AppleCrypto.cs	Updated factory method to use new class name
ECDsa.Create.AppleCrypto.cs	Updated factory method to use new class name
ECDiffieHellman.Create.AppleCrypto.cs	Updated factory method to use new class name
System.Security.Cryptography.csproj	Updated file references to use new naming convention
RSAAppleCrypto.macOS.cs	Renamed class definition from RSASecurityTransforms
RSAAppleCrypto.iOS.cs	Renamed class definition from RSASecurityTransforms
RSAAppleCrypto.cs	Renamed main class and constructors from RSASecurityTransforms
EccAppleCrypto.macOS.cs	Renamed class definition from EccSecurityTransforms
EccAppleCrypto.iOS.cs	Renamed class definition from EccSecurityTransforms
EccAppleCrypto.cs	Renamed main class and constructor from EccSecurityTransforms
ECDsaAppleCrypto.cs	Renamed class and updated field type from SecurityTransforms
ECDiffieHellmanAppleCrypto.cs	Renamed class, field type, and nested class from SecurityTransforms