Add service to update Dast::Profile

Background

a Dast::Profile is a description of how to run an on-demand dast scan. it is comproised of a name and description and is associated with both a DastSiteProfile and a DastScannerProfile.

What does this MR do?

this merge request introduces a new ee-specific service called Dast::Profiles::UpdateService that updates existing Dast::Profiles.

Why?

users should be able to make changes to existing profiles.

Notes

• this merge request introduces a so-called "dangling" change. this was necessary in order to keep iterating on the overarching feature, which has a number of inter-dependencies. waiting on these changes would block work and put the feature at-risk.
• there is an issue to unify dast namespaces #299398 (closed)

Related Issue(s)

• #295244 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry developer-facing and behind feature flag
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team