Rename and/or replace `coverage:report` script

**Is your feature request related to a problem? Please describe.**
Currently, if you want to have different nyc options for your Cypress tests (for example if you're using a different test runner for unit tests), the only way to pass custom options is to use the `coverage:report` script in `package.json`. This approach is problematic because it's essentially a magic script name—new developers coming on to a project would have no indication what this script is for. What's worse, because it's in `package.json`, you can't even add a code comment to explain it. Your only option is to add something to a README or other documentation and hope that people actually read it.

**Describe the solution you'd like**
The ideal solution would be to make this command (as well as nyc options in general) configurable in `cypress.json` instead of relying on a magic script.

But at the very least, I feel the script should be renamed to something that makes it clear that this is related to Cypress, such as `cypress:coverage:report`. The current name is completely generic, and sounds like it should be used by the developer for generating generalized coverage reports.

**Describe alternatives you've considered**
In theory one workaround for this situation is to simply set the desired nyc config in the project's global `.nycrc` and instead pass a custom config for the other (i.e., unit) test runner. But this is still problematic because it would still not be immediately obvious that the global `.nycrc` config is **actually** specific to Cypress (again, one cannot add comments to it because of the JSON format).

**Additional context**
Just to reiterate, this is chiefly for a scenario where a different nyc config is desired for different test runners.