Coveralls reporting not working

[holgerd77]

Discovered during a check on an nyc version update PR on the blockchain library that coveralls reporting is currently not working when using the scripts from the config library:
ethereumjs/ethereumjs-blockchain#97

Did some tests and can confirm that removing the all exec statements from both the coverage and the coveralls command fixes this.

[ryanio]

I suggest we remove coveralls functionality in this repo now that we can simply push to coveralls (or codecov, etc.) with GitHub Actions like so:

https://github.com/ethereumjs/ethereumjs-util/blob/3bbc948a1887df5f10fb0ebc3f07b7b9f774302c/.github/workflows/build.yml#L27-L30

I suggest we also consider removing coverage as well, since ideally each repo should automatically run their test suite with nycso a separate coverage command shouldn't be necessary:

https://github.com/ethereumjs/ethereumjs-util/blob/master/package.json#L20

Please let me know what you think :)

The more important part of the universal config to keep should be the nyc.json.

[holgerd77]

coveralls: yes, makes sense
coverage: not 100% sure but have a tendency to remove as well. That would mean we kill the whole package?

[ryanio]

Well, I think we can keep the nyc config