feat(croncontroller): Implement heap-based Schedule

[irvinlim]

Improves the performance of the CronController by switching to a min-heap instead of iterating all JobConfigs every second.

[codecov]

Codecov Report

Merging #95 (322f328) into main (6d36ac5) will increase coverage by 0.15%.
The diff coverage is 80.10%.

@@            Coverage Diff             @@
##             main      #95      +/-   ##
==========================================
+ Coverage   63.35%   63.50%   +0.15%     
==========================================
  Files         203      205       +2     
  Lines       10735    10958     +223     
==========================================
+ Hits         6801     6959     +158     
- Misses       3571     3621      +50     
- Partials      363      378      +15     

Impacted Files	Coverage Δ
...execution/controllers/croncontroller/controller.go	24.00% <0.00%> (-1.00%)	⬇️
...xecution/controllers/croncontroller/cron_worker.go	66.48% <70.87%> (-4.77%)	⬇️
pkg/execution/util/schedule/schedule.go	75.72% <75.72%> (ø)
pkg/utils/heap/heap.go	98.92% <98.92%> (ø)
pkg/execution/util/schedule/option.go	100.00% <100.00%> (ø)
...kg/execution/controllers/croncontroller/metrics.go	0.00% <0.00%> (-100.00%)	⬇️
pkg/runtime/reconciler/metrics.go	42.10% <0.00%> (-26.32%)	⬇️
pkg/execution/controllers/croncontroller/ticker.go	87.50% <0.00%> (-12.50%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6d36ac5...322f328. Read the comment docs.

[qingyuanz]

LGTM!