Aliases not being used while parsing contents of the `$ENV` file

## Steps to reproduce

create `$HOME/temp.env` -
```sh
alias echo=_echo
_echo() { printf '%s\n' 'You are using the alias'; }
echo You are NOT using the alias
```

Now run `ENV=$HOME/temp.env mrsh`

## Expected output
```
You are using the alias
```

## Actual output
```
You are NOT using the alias
```