Current `PluginOpt` code doesn't have the possibility of having a
different name for the parameter and the reference used in the code.

This would be the equivalent in arg parser to not having a `dest`
argument available to us.

This patch proposes a change to allow this using a new `PluginOpt` field
called `param_name`.

This new field will only be used when interfacing with users. In other
words, when showing the options to users (eg: `list_plugins`), when
parsing the command line arguments (eg: `_set_tunables`), and when
reading the config file (this doesn't require code changes because it
leverages the normal `_set_tunables` method).

Signed-off-by: Gorka Eguileor <[email protected]>

This patch makes 2 options settable globally and per-plugin: `maxhours`
and `all-logs`.

The `maxhours` option maps to what the code used to call `maxage`, which
has also been renamed to `maxhours` to be consistent.

Examples:

```
sos report --all-logs --maxhours=1
sos report -k container_log.all-logs=on,container_log.maxhours=1
sos report --all-logs --maxhours=1 \
  -k container_log.all-logs=off,container_log.maxhours=2
```

This adds flexibility to what users want to retrieve.

Signed-off-by: Gorka Eguileor <[email protected]>