[RUN AS-IF-FOSS] Fix invite team members link on projects page

What does this MR do?

• Addresses issues with project/group permissions found while investigating https://gitlab.com/gitlab-org/gitlab/-/issues/285021
• Moves code to the correct foss area (some code was in the ee area as there were some pages specific loading issues now resolved)
• Removes the feature specs in favor of lighter view specs
• Fixes feature specs around inviting that were uncovered due to fixing the original issue.

Note

No changelog since we are behind a disabled-in-production feature flag

How to test locally

• enable invite_members_group_modal globally via bundle exec rails console, then entering...

Feature.enable(:invite_members_group_modal)

• visit a group or project you are a maintainer or owner on. Then visit one where you are merely a developer or reporter to see the absence of the link.

Screenshots (strongly suggested)

area	invite team link	modal launch on click
project show
group show

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• 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

Related to #285021