Elements of `bytes constant` are not read-only

## Description
The compiler does not disallow modifying individual bytes of `bytes constant` variables.

The changes do not persist, but probably only due to the fact that each use of the constant reexecutes the initializer and allocates new memory to store the value.

## Environment

- Compiler version: 0.8.36

## Steps to Reproduce
```solidity
bytes constant B = "abc";

contract C {
function f() public returns (bytes memory) {
B[1] = "x"; // No compilation error
delete B[2]; // No compilation error
return B; // Still returns "abc"
}
}
```

For comparison, there are compile-time checks against doing the same with a fixed-bytes variable:
```solidity
bytes32 constant B32 = "abc";

contract C {
function f() public returns (bytes32) {
B32[1] = "x"; // Error: Single bytes in fixed bytes arrays cannot be modified.
delete B32[2]; // Error: Single bytes in fixed bytes arrays cannot be modified.
return B32;
}
}
```

Start by compiling the Solidity reproduction and compare the diagnostics for bytes constant with the existing fixed-bytes behavior. Trace the compiler path handling element assignment and delete for constant dynamic bytes values; done means both mutations are rejected while reading and returning B remains valid.

Written by the indexing model from the issue text.