[ACNA-1228][ACNA-1327] improve e2e tests with retry and exponential fallback

[florind-ens]

Description

Replaced deprecated request-promise-native with @adobe/aio-lib-core-networking for improved e2e tests which supports retry.

Related Issue

Fixes #77
Fixes #22

Motivation and Context

We run the e2e tests daily via the aio-e2e-tests repo. The connection to IMS sometimes fails because we can't exchange a jwt token, and we should be using aio-lib-core-networking to do a retry with fallback.

How Has This Been Tested?

By running e2e and unit tests.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #81 (63c12a2) into master (8cef01d) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #81   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            8         8           
  Lines          413       420    +7     
  Branches        50        51    +1     
=========================================
+ Hits           413       420    +7     

Impacted Files	Coverage Δ
src/ims.js	100.00% <100.00%> (ø)

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[Himavanth]

Just a minor comment. Otherwise LGTM. @shazron ?

[Himavanth]

LGTM @shazron ?