feat: support extracting package groups from v2+ poetry.lock files

[G-Rath]

Poetry v2 lockfiles now include the groups a package belongs to, meaning that we can support extracting them to allow filtering.

Similar to Maven and NPM, Poetry explicitly notes everything that isn't in an explicit group as being in the main group meaning for packages that are considered in that group we always use an empty slice instead since that's how we indicate the "production" group.

I generated the final fixture using the following pyproject.toml:

[project]
name = "mine"
version = "1.0.0"

requires-python = ">=3.9"

dependencies = [
  "proto-plus == 1.22.0; python_version >= '3.6' and python_version < '3.10'",
  "proto-plus == 1.23.0; python_version >= '3.10'",
  "six"
]

[project.optional-dependencies]
caching = ["redis>=1"]

[tool.poetry.group.dev.dependencies]
urllib3 = "*"
factory-boy = "*"

[tool.poetry.group.test.dependencies]
faker = "*"

Technically we don't need the python_version constraint on proto-plus for this feature, but I realised we don't have any existing fixtures for this situation so I figured I'd sneak it in as part of this given it seems like we already support the lockfile having a package multiple names with different versions

---

This is a sister PR to google/osv-scalibr#376 since osv-scanner is still in the middle of transitioning to using osv-scalibr - the core logic is exactly the same, and either (or both) should be fine to land

[G-Rath]

(fwiw I plan to port this to osv-scalibr tomorrow, so this might end up getting closed but the actual core implementation should still be reviewable)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.95%. Comparing base (729bb95) to head (c7b506f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1477      +/-   ##
==========================================
+ Coverage   66.93%   66.95%   +0.01%     
==========================================
  Files         197      197              
  Lines       18621    18632      +11     
==========================================
+ Hits        12464    12475      +11     
  Misses       5471     5471              
  Partials      686      686              

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