move matching logic into its own namespace

[williballenthin]

within main, we have a lot of code for finding capabilities: https://github.com/mandiant/capa/blob/master/capa/main.py#L122-L339

more than 200 lines for static analysis, and soon we'll have parallel implementations for dynamic analysis. this seems like too much code for the main script, which should probably be focused on handling CLI args and rendering the results.

we should move this logic into their own namespaces. this will be a breaking change for users that invoke capa as a library; however, its a good change for the long term health of capa.

[yelhamer]

this will be a breaking change for users that invoke capa as a library

Perhaps we could still provide an extract_capabilities() function in main that calls into the new namespace, for backwards-compatibility reasons.

[williballenthin]

good idea. we can survey the scripts in capa/scripts/* to see how they reach into capa.main and try to preserve some level of compatibility.

[mr-tz]

addressed as part of #1948?

[williballenthin]

closed in #1948