feat: implement dex module

[delvinru]

Hi, I have implemented the dex module.

The current version is incompatible with the old version, because in that implementation there were not very convenient methods and names of exported variables.

What has been changed:

• Added new method checksum for computing adler-32 checksum;
• Added new method signature for computing sha-1 signature;
• Added new methods: contains_strings, contains_methods, contains_classes - honestly, I doubt their usefulness, but I decided to leave them, because binary search is used under the hood, since the strings are guaranteed to be sorted by the format itself;
• Methods removed: has_method_string, has_method_and_class_string, has_method_regexp, has_method_and_class_regexp, has_class_string, has_class_regexp (as far as I can see on github, no one used them anyway); And in practice, quite useless calls;
• Changed access to strings, methods, types, protos and classes. I've made them more informative and user-friendly, unlike the previous implementation;
• Added documentation, because on https://yara.readthedocs.io / there is no information about dex module;

Fuzzing testing was started locally, all errors were fixed, but I do not exclude that something else will be revealed during a long run.

Since the most difficult thing in programming is to come up with a name for variables, if there are suggestions about names in proto, then I'm ready for discussion.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[plusvic]

Are all these fields xxxx_size and xxxx_off really useful? They look like the offset and size of certain sections within the files, are but I would avoid exposing to much data in the module of that data is seldom used in real-life YARA rules.

[delvinru]

I'm not sure about deleting these parameters, because sometimes you can build a rule on them.
In my opinion, we shouldn't delete this information, because in fact it is the header of the dex file and it is better to reflect it completely.

[delvinru]

@plusvic Hi, there are a lot of clippy errors in the pipeline that are not related to my code (or any my changes)

It's better to fix them in the master, and then merge them into this branch, rather than the other way around.