Replace deprecated pkg_resources with packaging.requirements

[junagent]

Summary

Replace pkg_resources.Requirement with packaging.requirements.Requirement in install_requirements_helper.py.

Problem

The file imports Requirement from the deprecated pkg_resources module:

from pkg_resources import Requirement

With setuptools 82 removing pkg_resources (PEP 740), this import will break on newer Python installations.

Fix

jina already has packaging>=20.0 as a core dependency, so the replacement is straightforward:

Before	After
from pkg_resources import Requirement	from packaging.requirements import Requirement
Requirement.parse(line)	Requirement(line)
.project_name	.name

The packaging.requirements.Requirement API is equivalent for parsing requirement strings and accessing name/extras attributes.

Note: The _is_requirements_installed function still uses pkg_resources.require() for runtime dependency checking. This is a separate concern and not changed in this PR.