test(stark-all): simplify karma configuration in stark-* packages + showcase

[SuperITMan]

ISSUES CLOSED: #1145

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#-commit-message-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

The custom karma configuration for packages is repeated in every stark packages (stark-core, stark-rbac, stark-ui). It's complex to maintain and require to change the Karma config in 3 locations, for now, everytime a change is needed.

The showcase contains useless custom aliases.

Issue Number: #1145

What is the new behavior?

Karma configurations for packages has been simplified and are written only once under "packages/karma.conf.js" and "packages/karma.conf.ci.js".

The showcase does not contain any custom aliases.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[coveralls]

Coverage decreased (-0.3%) to 94.066% when pulling 3866b7f on SuperITMan:bugfix/simplify-karma-config into 52ae6e0 on NationalBankBelgium:master.

[nicanac]

Nice, LGTM 👍