Convert all FF calls to beta_feature_available?

What does this MR do?

When merged in, didnt realize that feature_available? doesnt correctly scope the FF to the namespace as we expected it to. We needed to change all :wip_limits FF checks from ProjectOrGroup.feature_available? to ProjectOrGroup.beta_feature_available?

Also, given that when a user goes to issue boards on project or group, sometimes they go to the boards index route and sometimes the show which is why i needed to update the pushing of the frontend feature flag to be on :index and :show.

Documentation MR for this coming soon to avoid confusion in the future when FF'ing.

Repro instructions:

• rails c
• Pick a group or project to scope the FF to.
• Feature.enable(:wip_limits, group_or_project_you_have_selected)
• Then go to that project or group's issue board and make sure the gear icon appears.
• if you want to confirm the WIP Limits on the MR is working properly, you will need to set the max_issue_count on the group_or_project.boards.first.lists.find(list with list_type of label)

/cc @donaldcook @pderichs @mdelaossa @engwan

Screenshots

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

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