feat(@angular/build): add code coverage reporters option for unit-test

[clydin]

The experimental unit-test builder now contains an additional option named codeCoverageReporters that supports configuring the reporter(s) for code coverage results. This options only has an effect if the codeCoverage option is also enabled. The codeCoverageReporters is an array with elements that can be either a string or a tuple of a string and options object. The later form supports customizing individual reporters. The options object fields are not validated by the builder schema. This option currently only is used by the vitest runner.