Immutable variables treated differently depending on type

## Description

An immutable variable that is initialized at declaration site can be used in `pure` context if it is of type `uint` but not if it is of type `address`.

## Environment

- Compiler version: 0.8.29

## Steps to Reproduce

```solidity
// SPDX-License-Identifier: GPL-3.0

pragma solidity 0.8.29;

contract Test {
address internal immutable _a = 0x0000000000000000000000000000000000000001;
uint256 internal immutable _b = 42;

function a() external pure returns (address) {
return _a; // TypeError: Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
}

function b() external pure returns (uint256) {
return _b; // no error
}
}
```

Start by compiling the provided Solidity reproducer with compiler version 0.8.29 and compare the pure-context handling of the immutable uint and address variables. Trace the compiler path that classifies immutable reads, then add regression coverage showing consistent behavior for both types; done means the intended pure functions compile without an incorrect diagnostic.

Written by the indexing model from the issue text.