Allow compressing lima-guestagent with gzip

[afbjorklund]

Remove all compression configuration, and make it boolean.

         compressed        uncompressed  ratio uncompressed_name
           10829118            39059456  72.3% _output/share/lima/lima-guestagent.Linux-aarch64
           11190957            38797312  71.2% _output/share/lima/lima-guestagent.Linux-armv7l
           11431176            39387136  71.0% _output/share/lima/lima-guestagent.Linux-riscv64
           12076900            40189952  70.0% _output/share/lima/lima-guestagent.Linux-x86_64
           45528151           157433856  71.1% (totals)

Could become the default config (y), after some evaluation.

Replaces #2427
Closes #2426

[AkihiroSuda]

Thanks

[jandubois]

I feel like usrlocalsharelima.Open does not belong in that package because it has nothing to do with that location, but I don't have any other suggestion. Maybe fileutils?

Anyways, I'm fine with merging as-is.

[afbjorklund]

I can move the code back to pkg/cidata again, now that it is a lot smaller.

I wanted the compression to be abstract/local, but it leaked out anyway...

[afbjorklund]

Maybe fileutils?

Something like gzopen would have been nice to have.

gzopen can be used to read a file which is not in gzip format; in this case gzread will directly read from the file without decompression. When reading, this will be detected automatically by looking for the magic two-byte gzip header.

But I can't find the format detection (file magic) either?

i.e. it is also missing from the compress/gzip module

[jandubois]

The logic seems correct, but I would prefer a simplified expression that keeps the error handling close to the location the error occurred.

[jandubois]

Thanks, LGTM