pending API to expose the state of asynchronous icache setters

[agubler]

Type: feature

The following has been addressed in the PR:

• There is a related issue
• All code has been formatted with prettier as per the readme code style guidelines
• Unit or Functional tests are included in the PR

Description:

In order to be able to determine the status of an async icache.set/icache.getOrSet this new API, .pending returns if the promise is still unresolved.

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[codecov]

Codecov Report

Merging #862 (3bcaa6f) into master (e74d23b) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #862   +/-   ##
=======================================
  Coverage   94.71%   94.71%           
=======================================
  Files         127      127           
  Lines        8084     8087    +3     
  Branches     1884     1885    +1     
=======================================
+ Hits         7657     7660    +3     
  Misses        427      427           

Impacted Files	Coverage Δ
src/core/middleware/icache.ts	100.00% <100.00%> (ø)

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