Comparison of a fixed type and a rational literal is not commutative

## Description

```solidity
function fixed_number_test(fixed num) {
// Compiles
if (num > 2.5) {}
// Does not compile
if (2.5 < num) {}
}
```

When comparing a fixed/ufixed number and a rational literal, the Solidity compiler compiles the code when the fixed number is on the LHS side, but it doesn't when LHS and RHS are swapped.

## Environment

- Compiler version: `0.8.18+commit.87f61d96.Linux.g++`
- Target EVM version (as per compiler settings): default
- Framework/IDE (e.g. Truffle or Remix): Direct invocation from CLI (`solc test.sol`)
- EVM execution environment / backend / blockchain client: N/A
- Operating system: Ubuntu 22.04.2 LTS server

## Steps to Reproduce

Save the above code as `test.sol` and run `solc test.sol`. Line 3 compiles, but line 5 fails to compile with message "Built-in binary operator < cannot be applied to types rational_const 5 / 2 and fixed128x18. Fractional literals not supported."

I expect Solidity to treat both lines equally.

Reproduce the fixed_number_test example in test.sol by running solc test.sol, then compare the diagnostics for the two operand orders. Trace the Solidity compiler's type-checking path for binary comparisons; done means both comparisons are handled consistently and the behavior is covered by a regression test.

Written by the indexing model from the issue text.