Add sync and wait to durable promise class

[dfarr]

Sync and wait can be used to join on the completion of a durable promise. Sync resolves when the durable promise completed, wait resolves to the value (or throws a corresponding error) when the durable promise is completed.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 52.94118% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 80.74%. Comparing base (93ad425) to head (d4e4b4d).

Files	Patch %	Lines
lib/core/promises/promises.ts	50.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #112      +/-   ##
==========================================
- Coverage   81.17%   80.74%   -0.44%     
==========================================
  Files          22       22              
  Lines        1307     1319      +12     
  Branches      331      355      +24     
==========================================
+ Hits         1061     1065       +4     
- Misses        238      246       +8     
  Partials        8        8              

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