fix(wasm): don't kill task on drop

[maan2003]

makes behavior similar to tokio::spawn otherwise spawned tasks immediately die if join handles are not saved somewhere

[maan2003]

cc @jplatte

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 85.37%. Comparing base (2657eb7) to head (3818d1c).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/matrix-sdk-common/src/executor.rs	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4572      +/-   ##
==========================================
- Coverage   85.39%   85.37%   -0.02%     
==========================================
  Files         286      286              
  Lines       32229    32235       +6     
==========================================
  Hits        27522    27522              
- Misses       4707     4713       +6     

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[Hywan]

This comment must be elaborated to explain why we don't abort the future when the join handle is dropped:

• Why?
• Does it match the Tokio's behaviour?

Thanks.

[Hywan]

Thanks for your contribution :-).

It would be nice if you could address my comment, and if tests could be added. This is an important change.