change to next method as synchronously

[easylogic]

What this PR does / why we need it?

Replace all of the eventStreamObserver.next() functions with synchronous forms.

• Prevents incorrect data updates when eventers run asynchronously.
• Clarify when async events are fired when using them.

Any background context you want to provide?

What are the relevant tickets?

Fixes #525

Checklist

• Added relevant tests or not required
• Didn't break anything

[codecov]

Codecov Report

Merging #526 (ae66828) into main (5f508e1) will decrease coverage by 2.05%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##             main     #526      +/-   ##
==========================================
- Coverage   90.21%   88.17%   -2.05%     
==========================================
  Files          70       77       +7     
  Lines        6153     7397    +1244     
  Branches      578      714     +136     
==========================================
+ Hits         5551     6522     +971     
- Misses        387      603     +216     
- Partials      215      272      +57     

Impacted Files	Coverage Δ
src/util/observable.ts	36.36% <41.66%> (-7.06%)	⬇️
src/document/document.ts	73.41% <100.00%> (+1.26%)	⬆️

... and 25 files with indirect coverage changes

[chacha912]

Thanks for your contribution. It looks good :)

[hackerwins]

Thanks for your contribution.