[L] Change in flashrom[master]: flashrom_tester: Rewrite IOOpts to support more operations

[Peter Marheine (Code Review)]

Attention is currently required from: Evan Benn.

Peter Marheine has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/71973 )

Change subject: flashrom_tester: Rewrite IOOpts to support more operations
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Patch Set 6:

(2 comments)

File util/flashrom_tester/flashrom/src/cmd.rs:

https://review.coreboot.org/c/flashrom/+/71973/comment/0163f94a_ba6792d3 
PS4, Line 82:     // an operation must provide a file or a region.file or both.
> I think you are saying some things I get and some that I dont, I have had another attempt PTAL. […]

It's moving in a direction that makes more sense; comments on the changes.

File util/flashrom_tester/flashrom/src/cmd.rs:

https://review.coreboot.org/c/flashrom/+/71973/comment/fe78b8a6_5058d806 
PS6, Line 73: Option
This still seems weird, in that it's required to specify either a file or a region with some file. It seems like we want to express these cases:

* One file, entire chip
 * One file, part of chip
 * Multiple files, one per part of chip

..which can be translated to a type in a pretty straighforward way once we've enumerated the options that make sense:

```
enum FileIoMapping {
    /// Operate on the entire flash, mapped to an entire file.
    CompleteImage(Path),
    /// Operate on the named flash regions only, mapped to the corresponding portions of
    /// the given file.
    PartialImage(Path, &[&str]),
    /// Operate on the named flash regions, mapping each to a single file.
    FilePerRegion(&[(Path, &str)]),
}
```

It could also then move the layout into the variants that operate on regions, to capture that layout only matters if you're not operating on the complete flash.