Optimize EVM stack push operations with SIMD and source generation

[Copilot]

Changes

Source Generator Implementation

• Added StackPushBytesGenerator and GenerateStackOpcodeGenerator to auto-generate optimized push methods for byte sizes 1-32
• Eliminated runtime size checks and branching through compile-time specialization
• Generated methods use [GenerateStackPushBytes(size, PadDirection)] attribute

SIMD Stack Operations

• Replaced generic Span.CopyTo with direct Vector256<byte>/Vector128<byte> construction
• Added CopyUpTo32 helper using unaligned SIMD reads for optimal byte copying
• Single 32-byte stores replace multiple smaller writes
• Specialized paths for common sizes (1, 2, 4, 8, 16 bytes)

VM Execution Loop

• Simplified opcode dispatch using nuint indexing with function pointers
• Removed special-case POP inlining (now uniform dispatch)
• Moved opcode count tracking to exception paths only

API Changes

• Push methods now return EvmExceptionType instead of void for unified error handling
• Added PushBytesNullableRef for stack overflow detection without exceptions
• Explicit PushZero/PushOne methods replace conditional pushes

Before:

stack.PushBytes<TTracingInst>(immediateData);  // Generic copy

After:

stack.Push8Bytes<TTracingInst>(ref bytes);  // Generated SIMD implementation

Types of changes

What types of changes does your code introduce?

• Optimization

Testing

Requires testing

• No

Documentation

Requires documentation update

• Yes
• No

Requires explanation in Release Notes

• Yes
• No

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[benaadams]

Seems excessive