Add array_like (de)serialization for dataclasses

[mishamsk]

Hi!

Wanted to float an idea of adding "array_like" serialization format for data classes. Essentially the same as this msgspec feature.

As of time of writing this is just a POC, see this single new test for a sample.

Such an option will be a big size reduction/performance boost, but the interaction with other options will be pretty tricky. At least the discrimination and defaults handling will have to be carefully handled. Some configuration combinations will have to be forbidden (e.g. skipping defaults with array_like enabled).

Wanted to get some feedback early before doing the entire thing, hence opening PR so early.

[pep8speaks]

Hello @mishamsk! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file mashumaro/core/meta/code/builder.py:

Line 1385:80: E501 line too long (80 > 79 characters)
Line 1391:80: E501 line too long (80 > 79 characters)

• In the file tests/test_config.py:

Line 389:1: E302 expected 2 blank lines, found 1