Replace istanbul with nyc

[cgewecke]

Description

Istanbul has been deprecated.

Before we were combining runs by renaming folders and using a special merge tool. nyc's report command does this automatically if the different tests are run with --no-clean.

Also, in removing either istanbul or istanbul-combine, we lost a dependency called regenerator-runtime which the build was relying on see broken browser tests. Have added it as a dev dep.

Resources

nyc docs

Type of change

• Dependency fix (non-breaking change)

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run dtslint with success and extended the tests and types if necessary.
• I ran npm run test:unit with success and extended the tests if necessary.
• I ran npm run build-all and tested the resulting file/'s from dist folder in a browser.
• I have updated the CHANGELOG.md file in the root folder.
• I have tested my code on the live network.

[coveralls]

Coverage remained the same at 84.757% when pulling fba6838 on ci/nyc into 5b8c12e on 1.x.

[nivida]

LGTM! 🎊