feat: decouple sync and async operators

[codecov-commenter]

Codecov Report

Base: 97.44% // Head: 97.59% // Increases project coverage by +0.14% :tada:

Coverage data is based on head (6d5028e) compared to base (92b51f3). Patch coverage: 99.30% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #219 +/- ## ========================================== + Coverage 97.44% 97.59% +0.14% ========================================== Files 49 54 +5 Lines 1647 1828 +181 Branches 340 341 +1 ========================================== + Hits 1605 1784 +179 - Misses 42 43 +1 - Partials 0 1 +1 ``` | [Impacted Files](https://codecov.io/gh/vitaly-t/iter-ops/pull/219?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [src/ops/on-end.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL29wcy9vbi1lbmQudHM=) | `48.14% <85.71%> (+1.99%)` | :arrow_up: | | [src/ops/timeout.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL29wcy90aW1lb3V0LnRz) | `58.82% <85.71%> (+2.57%)` | :arrow_up: | | [src/ops/reduce.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL29wcy9yZWR1Y2UudHM=) | `96.61% <95.55%> (-3.39%)` | :arrow_down: | | [src/entry/async.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL2VudHJ5L2FzeW5jLnRz) | `100.00% <100.00%> (ø)` | | | [src/entry/index.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL2VudHJ5L2luZGV4LnRz) | `100.00% <100.00%> (ø)` | | | [src/entry/sync.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL2VudHJ5L3N5bmMudHM=) | `100.00% <100.00%> (ø)` | | | [src/index.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL2luZGV4LnRz) | `100.00% <100.00%> (ø)` | | | [src/ops/aggregate.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL29wcy9hZ2dyZWdhdGUudHM=) | `100.00% <100.00%> (ø)` | | | [src/ops/async/delay.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL29wcy9hc3luYy9kZWxheS50cw==) | `100.00% <100.00%> (ø)` | | | [src/ops/async/retry.ts](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL29wcy9hc3luYy9yZXRyeS50cw==) | `100.00% <100.00%> (ø)` | | | ... and [64 more](https://codecov.io/gh/vitaly-t/iter-ops/pull/219/diff?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None)

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[vitaly-t]

Sorry, I didn't have the time this needs to review properly, before merging into master, so I merged into the fresh v4 branch instead, so it doesn't hang in dev.

[vitaly-t]

And I published it as v4.0.0-beta.1, from branch v4.