"UI" improvements: move more config files + allow multiple & inline

It's clear that adding more command-line options aren't the path forward. What I suggest instead is that everything (or almost everything?) should be possible to specify as a parameter in a config file. All current command line options will internally translate to a hidden config file. Furthermore, one should be able to load multiple config files, to enable refactoring. Finally, it most be possible to give an inline config files as command line option. Example:

```
dromajo base.cfg -c '{ "resetvector" = "0x1000" }'
```

The config files are loaded in-order, such that later ones can override earlier ones. Finally, inline configs are loaded last.

Start by tracing Dromajo's command-line option parsing and existing configuration-file loading, since the issue names no files or tests. Determine how current options become configuration values and how files are parsed. Done means multiple files load in order, later values override earlier ones, and an inline configuration is applied last.

Written by the indexing model from the issue text.