Fix registry already registered check

[yycptt]

What changed?
Also check chained registry when checking if an activity/workflow function is already registered.

Why?
Also check chained registry when checking if an activity/workflow function is already registered.

How did you test it?
Unit test.

Potential risks
in the worst case, the already registered check maybe broken, causing register function to fail or panic.

[coveralls]

Pull Request Test Coverage Report for Build 5a9ee3f6-bbb0-42d7-8b38-3feedd410706

• 11 of 11 (100.0%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.03%) to 74.819%

---

Files with Coverage Reduction	New Missed Lines	%
internal/internal_task_pollers.go	2	75.25%

Totals
Change from base Build 438753a1-0d24-4662-8662-b8c1982f371f:	0.03%
Covered Lines:	9612
Relevant Lines:	12847

---

💛 - Coveralls