Implement User-side Config for Build Tasks (ZAP scans, et al)

[drewbo]

Decide how configuration of a build task should be handled in the UI + task itself.

Acceptance Criteria

• Determine next steps and acceptance criteria

[apburnes]

Defer to a later date once we have user data on how the build tasks could be configurable.

[sknep]

See #4170 and #4171

[drewbo]

Two WIP PRs up for this:

• Feat build scan config #4531 implements the ability for users to configure their scan rules at site/:id/scan-config. The functionality is there and it could use a healthy does of styling
• Use scan configuration pages-cf-build-tasks#33 adds the supplied configuration to the scans and changes the data processing to ignore rules as specified. It does not yet change the rendering of the reports

cc: @sknep