Feature Request: Macro Validation Ignorelist

[ljstella]

Relevant discussion: https://splunk-usergroups.slack.com/archives/C78NT6CQ7/p1710531076795219

It may make sense to supply via the contentctl.yml config a list of macros that are expected to be present on a system but may not be packaged directly in the generated app. This allows for macros bundled in other apps to be utilized without being wrapped in another macro just for inclusion here. We may want to also consider a more complex macro object in the list allowing for notes about what app the macro is present in, or some form of stub that can be placed in the macros/ directory.

[pyth0n1c]

I am going to add lookups/ as an additional request here as well, since many apps ship common lookups that we may wish to ignore as well.