Use ActiveRecord Enum labels in current filters status

[harunkumars]

Fixes Issue #3157 - Display Enum labels for Active Filters in Current Search Status

ActiveAdmin::Filters::ActiveFilter#values controls the displayed value for active filters.
This currently does not have any special handling for Enums.

For e.g. with an enum definition like enum status: [:inactive, :active] , when filtering for :inactive status, the Current Search Status widget shows "Status is 0"

This PR, uses ActiveRecord::Enum.defined_enums to translate the display value for the filter to the associated label for enums. The Current Search Status widget will now show "Status is Inactive"

If a custom collection is provided when registering the ActiveAdmin resource e.g. filter :status, as: :select, collection: [[:not_active, 0], [:active, 1]] which specifies dropdown labels that are different from the enum labels, then the dropdown label from the custom collection is used. The Current Search Status widget will now show "Status is Not Active"

Sample before and after screenshots attached:
Before Fix:

After Fix:

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (25c74c7) 98.92% compared to head (0221992) 98.93%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7790   +/-   ##
=======================================
  Coverage   98.92%   98.93%           
=======================================
  Files         197      197           
  Lines        4950     4963   +13     
=======================================
+ Hits         4897     4910   +13     
  Misses         53       53           

Impacted Files	Coverage Δ
lib/active_admin/filters/active_filter.rb	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[Aesthetikx]

Great work on this @harunkumars, thank you!