Add methods for the persistent cache Agent interface

[ofek]

Motivation

About to use it and realized the interface could be simplified since you'd want to utilize the unique check ID in all cases

integrations-core/win32_event_log/datadog_checks/win32_event_log/check.py

Lines 252 to 263 in bafe92c

	def update_bookmark(self, event):
	# See https://docs.microsoft.com/en-us/windows/win32/wes/bookmarking-events
	# https://docs.microsoft.com/en-us/windows/win32/api/winevt/nf-winevt-evtupdatebookmark
	# http://timgolden.me.uk/pywin32-docs/win32evtlog__EvtUpdateBookmark_meth.html
	win32evtlog.EvtUpdateBookmark(self._bookmark_handle, event)
	# https://docs.microsoft.com/en-us/windows/win32/api/winevt/nf-winevt-evtrender
	# http://timgolden.me.uk/pywin32-docs/win32evtlog__EvtRender_meth.html
	bookmark_xml = win32evtlog.EvtRender(self._bookmark_handle, win32evtlog.EvtRenderBookmark)
	self.write_persistent_cache('bookmark', bookmark_xml)

[codecov]

Codecov Report

Merging #6819 into master will increase coverage by 3.52%.
The diff coverage is n/a.

Impacted Files	Coverage Δ
disk/tests/common.py	64.28% <0.00%> (-35.72%)	⬇️
disk/tests/conftest.py	85.71% <0.00%> (-11.43%)	⬇️
disk/datadog_checks/disk/disk.py	82.80% <0.00%> (-3.61%)	⬇️
disk/tests/test_filter.py	96.45% <0.00%> (-3.55%)	⬇️
dns_check/datadog_checks/dns_check/dns_check.py	86.45% <0.00%> (-2.09%)	⬇️
...cks_base/datadog_checks/base/utils/agent/common.py
postgres/tests/test_relations.py
...tadog_checks_base/datadog_checks/base/stubs/log.py
mcache/tests/metrics.py
envoy/datadog_checks/envoy/envoy.py
... and 635 more

[therve]

That looks fine, though I only use it with the check ID for SNMP, wondering if we could make the key optional.

[ofek]

I think the key is a good way to not dump everything in a json blob