Avoid exceptions in environment diagnostics

[Rich Chiodo (rchiodo)]

Summary

• avoid raising AttributeError while probing sys.real_prefix
• use the Python 3.10+ standard-library importlib.metadata API instead of probing for the backport
• verify environment diagnostics do not emit debugpy-internal exceptions

Fixes #2058

Tests

• python -m pytest -q -o addopts='' tests\debugpy\test_log.py::test_environment_description_does_not_raise_internal_exceptions 'tests\debugpy\test_exception.py::test_vsc_exception_options_raise_with_except[program-launch--raised]'
• python -m black --check src\debugpy\common\log.py tests\debugpy\test_log.py
• python -m ruff check src\debugpy\common\log.py tests\debugpy\test_log.py

[Stella Huang (StellaHuang95)]

🔒 Automated review in progress — Stella Huang (@StellaHuang95) is auto-reviewing this PR.

[Stella Huang (StellaHuang95)]

Approved via Review Center.

[Stella Huang (StellaHuang95)]

Approved via Review Center.