test: add ut for pkg/wasm

[ChloroplastYu]

What this PR does:
add ut for pkg/wasm

Related issue:
#105

Does this PR introduce a user-facing change?:

NONE

[github-actions]

Hi @ChloroplastYu. Thanks for your PR! 🎉
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[ChloroplastYu]

@zhenjunMa please review, thank you!

[codecov]

Codecov Report

Attention: 115 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
components/custom/registry.go	84.00% <100.00%> (ø)
components/hello/helloworld/helloworld.go	100.00% <100.00%> (ø)
components/pluggable/config.go	100.00% <100.00%> (ø)
components/pluggable/register.go	100.00% <100.00%> (ø)
pkg/runtime/secretstores/factory.go	100.00% <100.00%> (ø)
pkg/runtime/secretstores/registry.go	100.00% <100.00%> (ø)
pkg/wasm/abi.go	8.69% <ø> (ø)
pkg/wasm/dispatch.go	100.00% <ø> (+76.19%)	⬆️
pkg/wasm/factory.go	73.24% <100.00%> (+48.88%)	⬆️
pkg/wasm/filter.go	61.11% <ø> (+61.11%)	⬆️
... and 8 more

📢 Thoughts on this report? Let us know!.

[ChloroplastYu]

/cc @zhenjunMa

[Xunzhuo]

/lgtm
/approve

Great job. Thanks for working on it.