`bytes.concat` is not allowed in constant initializers

[ItsNickBarry]

Description

bytes.concat does not work when defining constants.

Environment

• Compiler version: 0.8.21
• Target EVM version (as per compiler settings): Hardhat default
• Framework/IDE (e.g. Truffle or Remix): Hardhat
• EVM execution environment / backend / blockchain client: N/A
• Operating system: Ubuntu

Steps to Reproduce

This code compiles:

contract Test {
    bytes32 internal constant A = bytes32('a');
    bytes32 internal constant B = bytes32('b');
    bytes internal constant AB = abi.encodePacked(A, B);
}

This does not:

contract Test {
    bytes32 internal constant A = bytes32('a');
    bytes32 internal constant B = bytes32('b');
    bytes internal constant AB = bytes.concat(A, B);
}