gh-103143: Polish pdb help messages and doc strings (GH-103144)

* Made all the command part of the docstring match the official documentation
* Always have a space between the command and the description in docstring
* Added a helper function to format the help message

Before:

```
(Pdb) h a
a(rgs)
        Print the argument list of the current function.
(Pdb) h commands
commands [bpnumber]
        (com) ...
        (com) end
        (Pdb)
        ...
(Pdb) h interact
interact

        Start an interactive interpreter whose global namespace
        contains all the (global and local) names found in the current scope.
```

After
```
(Pdb) h a
      Usage: a(rgs)
      
      Print the argument list of the current function.
(Pdb) h commands
      Usage: (Pdb) commands [bpnumber]
             (com) ...
             (com) end
             (Pdb)
             ...
(Pdb) h interact
      Usage: interact
      
      Start an interactive interpreter whose global namespace
      contains all the (global and local) names found in the current scope.
```

Automerge-Triggered-By: GH:brandtbucher