Regression from v2.0.10 to 2.2/`devel` in `const` with `cstring`/`string` literal conversion: context: `n.nim(2, 21) Error: type mismatch: got 'cstring' for '""' but expected 'string'`
### Description

```nim
template g(_: int): string = ""
const c: cstring = 0.g()
```

### Nim Version

Builds:
```
Nim Compiler Version 2.0.10 [Linux: amd64]
Compiled at 2024-10-13
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: e941ee15be775fe3c46db1bed9b4f41c7dfb1334
active boot switches: -d:release
```

Does not build:
```
Nim Compiler Version 2.2.0 [Linux: amd64]
Compiled at 2024-10-13
Copyright (c) 2006-2024 by Andreas Rumpf

git hash: 78983f1876726a49c69d65629ab433ea1310ece1
active boot switches: -d:release
```

```
Nim Compiler Version 2.2.1 [Linux: amd64]
Compiled at 2024-10-13
Copyright (c) 2006-2024 by Andreas Rumpf

git hash: 720d0aee5c2d56260587f9ab09220d18ab9b53f7
active boot switches: -d:release
```

### Current Output

```text
/tmp/n.nim(2, 21) Error: type mismatch: got 'cstring' for '""' but expected 'string'
```


### Expected Output

_No response_

### Known Workarounds

_No response_

### Additional Information

_No response_