Add config setting to toggle memory usage runtime metrics.

[umaannamalai]

The Python Agent reports a large volume of memory usage related metrics because it sends data up for each PID. This PR adds a setting to allow users to toggle memory usage metrics (per PID only) reporting to reduce overall metrics being sent.

[github-actions]

🦙 MegaLinter status: ❌ ERROR

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ PYTHON	bandit	3		0	5.51s
✅ PYTHON	black	4	1	0	2.11s
✅ PYTHON	flake8	4		0	0.94s
✅ PYTHON	isort	4	2	0	0.26s
❌ PYTHON	pylint	4		7	8.74s

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[hmstepanek]

There's a couple lint errors but otherwise looks good:

  /github/workspace/newrelic/core/config.py:142:1: E302 expected 2 blank lines, found 1
  /github/workspace/tests/agent_unittests/test_sampler_metrics.py:174:1: W391 blank line at end of file