Improve vulnerability project GraphQL queries and error message

What does this MR do?

On the group-level and instance-level vulnerability report:

Group level	Instance level

The projects for the group/instance are fetched through GraphQL. This MR does the following:

1. Change a GraphQL error message from a function that returns a constant string, to just the constant string.

2. Rename the GraphQL queries to make it more obvious what they are for.

3. Pare down the properties that we're requesting through GraphQL to only those that are needed.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this is refactor work.
• 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