feat(AudienceEvaluator): Add the ability to provide custom condition evaluators

[jamesopti]

Summary

This PR (replacing #216) adds the ability for an SDK consumer to pass their own set of condition evaluators when creating an optimizely instance.

The core motivator for this is to be able to evaluate WEB audience conditions using the Javascript SDK as part of the EDGE project (go/edge).

Future fullstack use cases for this functionality might include audience condition plugins, where the customer would define their own match types and provide their own matchers.

/**
 * Condition evaluators for conditions that can be evaluated in a Cloudflare worker using
 * information like cookies, query parameters, userAgent, etc...
 */
function getConditionEvaluators(inputs) {
  return {
    cookies: {
      evaluate: matchCookies.match.bind(this, { cookies: inputs.cookies }),
    },
    device: {
      evaluate: matchDevice.match.bind(this, { device: Detect.parseUA(inputs.ua).device }),
    },
    ...
    /* Other custom condition evaluators */
  }
}

var optlyInstance = optimizely.createInstance({
  datafile: datafile,
  conditionEvaluators: getConditionEvaluators(inputs),
  skipJSONValidation: true
});

Test plan

Fixed existing tests. May need to add more unit tests.

Issues

https://optimizely.atlassian.net/browse/CJS-3034

[coveralls]

Coverage decreased (-0.07%) to 97.531% when pulling 4da5d4a on james/custom_condition_evaluators_OG into bd49de0 on master.

[lpappone]

delete? because we're handling this in typeToEvaluate - we only call this if there's a type.

[mjc1283]

Instead of passing logger, we can import a singleton logger and use it directly (example from project_config_manager)

[mikeproeng37]

+1

[mikeproeng37]

Mostly looks good. I just have a question.

[mikeproeng37]

+1