When handling internal function pointers, information loss can occur.

### Describe the issue:

When handling internal function pointers, information about function visibility (internal, external) can be lost.

### Code example to reproduce the issue:

```solidity
contract C {
function() internal returns (uint) a;
}
```

### Version:

0.10.3

### Relevant log output:

```shell
The type of a is as follows:
variable.type: function() returns(uint256)

However, I think it should be function() internal returns(uint256)
```

Start by reproducing the issue with the Solidity contract shown in the report on version 0.10.3, then trace how Slither represents and reports internal function pointers. The work is done when the reported type preserves the function's internal visibility, including the returns(uint256) signature.

Written by the indexing model from the issue text.