FIX: Run scheduled problem checks even when no tracker exists yet (#35102)

### What is this change?

Scheduled problem checks without trackers weren't being run. This is
because we directly tried to look for trackers instead of going through
the checks.

app/jobs/scheduled/run_problem_checks.rb

@@ -10,21 +10,17 @@ module Jobs
     every 10.minutes
 
     def execute(_args)
-      scheduled_checks =
-        ProblemCheckTracker.all.filter_map do |tracker|
-          tracker.check if eligible_for_this_run?(tracker)
+      ProblemCheck.scheduled.filter_map do |check|
+        if eligible_for_this_run?(check)
+          Jobs.enqueue(:run_problem_check, check_identifier: check.identifier.to_s)
         end
-
-      scheduled_checks.each do |check|
-        Jobs.enqueue(:run_problem_check, check_identifier: check.identifier.to_s)
       end
     end
 
     private
 
-    def eligible_for_this_run?(tracker)
-      tracker.check.present? && tracker.check.enabled? && tracker.check.scheduled? &&
-        tracker.ready_to_run?
+    def eligible_for_this_run?(check)
+      check.enabled? && check.scheduled? && check.ready_to_run?
     end
   end
 end

app/models/problem_check.rb

@@ -112,6 +112,11 @@ class ProblemCheck
     Collection.new(checks.select(&:realtime?))
   end
 
+  def self.tracker(target = NO_TARGET)
+    ProblemCheckTracker[identifier, target]
+  end
+  delegate :tracker, to: :class
+
   def self.identifier
     name.demodulize.underscore.to_sym
   end
@@ -137,6 +142,11 @@ class ProblemCheck
   end
   delegate :inline?, to: :class
 
+  def self.ready_to_run?
+    tracker.ready_to_run?
+  end
+  delegate :ready_to_run?, to: :class
+
   def self.call(data = {})
     new(data).call
   end
@@ -180,10 +190,6 @@ class ProblemCheck
 
   private
 
-  def tracker(target = NO_TARGET)
-    ProblemCheckTracker[identifier, target]
-  end
-
   def targets
     [NO_TARGET]
   end

spec/jobs/run_problem_checks_spec.rb

@@ -31,6 +31,17 @@ RSpec.describe Jobs::RunProblemChecks do
     ProblemCheck.send(:remove_const, "DisabledCheck")
   end
 
+  context "when a tracker hasn't been created yet" do
+    it "still schedules checks" do
+      expect_enqueued_with(
+        job: :run_problem_check,
+        args: {
+          check_identifier: "scheduled_check",
+        },
+      ) { described_class.new.execute([]) }
+    end
+  end
+
   context "when the tracker determines the check is ready to run" do
     before do
       ProblemCheckTracker.create!(identifier: "scheduled_check", next_run_at: 5.minutes.ago)