Add Image Pull Policy Docs

This is an initial skeleton of the docs, a lot of TBDs that will be resolved by other issues in the epic.

Preview: https://repo1.dso.mil/platform-one/big-bang/bigbang/-/blob/micah.nagel-master-patch-60517/docs/guides/using_bigbang/image_pull_policy.md

Closes https://repo1.dso.mil/platform-one/big-bang/bigbang/-/issues/915

changed milestone to %1.21.0

added kinddocs statusreview labels

assigned to @micah.nagel

changed the description

mentioned in issue #914 (closed)

mentioned in issue #912 (closed)

mentioned in issue #911 (closed)

mentioned in issue #910 (closed)

mentioned in issue #908 (closed)

approved this merge request

merged

mentioned in commit 5d786218

changed milestone to %1.20.0