refactor: remove unnecessary new Promise wrappers

[JKRhb]

This PR contributes to resolving #569. There are a few instances of the return Promise pattern left that were a bit difficult to resolve, though, so I am not sure whether we should keep the issue open?

[codecov]

Codecov Report

Attention: 64 lines in your changes are missing coverage. Please review.

Comparison is base (7cbe593) 75.54% compared to head (3489ea5) 75.67%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1110      +/-   ##
==========================================
+ Coverage   75.54%   75.67%   +0.12%     
==========================================
  Files          80       80              
  Lines       16164    16118      -46     
  Branches     1513     1507       -6     
==========================================
- Hits        12211    12197      -14     
+ Misses       3914     3882      -32     
  Partials       39       39              

Files	Coverage Δ
packages/binding-http/src/http-server.ts	83.30% <100.00%> (+0.05%)	⬆️
packages/binding-netconf/src/async-node-netconf.ts	54.76% <ø> (-1.06%)	⬇️
packages/binding-netconf/src/netconf-client.ts	65.55% <100.00%> (+0.17%)	⬆️
packages/binding-http/src/http-client-impl.ts	66.26% <82.35%> (-0.33%)	⬇️
packages/binding-mbus/src/mbus-client.ts	66.66% <50.00%> (+3.44%)	⬆️
packages/binding-mqtt/src/mqtt-client.ts	75.24% <0.00%> (+1.10%)	⬆️
packages/cli/src/cli-default-servient.ts	70.73% <10.52%> (+1.35%)	⬆️
packages/binding-file/src/file-client.ts	27.95% <0.00%> (+2.71%)	⬆️

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[danielpeintner]

I looked trough the changes and they seem all fine by me 👍

I would also argue after merging this PR we should close #569.

[relu91]

Looks good! regarding the issue linked, I think it might be difficult to be sure that every non-necessary promise it has been removed. I remember finding an eslint extension... maybe we could resolve it once the extension is in place and the non-convertible cases are correctly opted out.

[relu91]

Given we have two approvals I'm merging, let's wait for the eslint rule before closing #569

[JKRhb]

Looks good! regarding the issue linked, I think it might be difficult to be sure that every non-necessary promise it has been removed. I remember finding an eslint extension... maybe we could resolve it once the extension is in place and the non-convertible cases are correctly opted out.

That sounds good :) I updated the PR description before your merge so that #569 will stay open.