Rename admin/accounts_helper to admin/filter_helper (#1816)

- Add some spec coverage for both methods
- Add explicit constant call-outs for where the params are from

spec/helpers/admin/accounts_helper_spec.rb

@@ -1,5 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe Admin::AccountsHelper, type: :helper do
-
-end

spec/helpers/admin/filter_helper_spec.rb

@@ -0,0 +1,20 @@
+require 'rails_helper'
+
+describe Admin::FilterHelper do
+  it 'Uses filter_link_to to create filter links' do
+    params = ActionController::Parameters.new(
+      { test: 'test' }
+    )
+    allow(helper).to receive(:params).and_return(params)
+    allow(helper).to receive(:url_for).and_return('/test')
+    result = helper.filter_link_to('text', { resolved: true })
+
+    expect(result).to match(/text/)
+  end
+
+  it 'Uses table_link_to to create icon links' do
+    result = helper.table_link_to 'icon', 'text', 'path'
+
+    expect(result).to match(/text/)
+  end
+end