Tilde not expanded in paths

**Describe the bug**
I've noticed a variety of places where `cabal-install` accepts paths (e.g. on the command-line) yet doesn't expand tilde as is typical.

**To Reproduce**
Steps to reproduce the behavior:

```
$ cabal v2-install cabal-install --installdir=~/.cabal/bin
Resolving dependencies...
Up to date
~/.cabal/bin: createDirectory: does not exist (No such file or directory)
```
I know there have been other cases although I can't think of them off-hand.

**Expected behavior**
The path `~/.cabal/bin` be expanded to `$HOME/.cabal/bin`.

**System information**
- NixOS 20.03
- `cabal-install` 3.2.0.0