feat(FEC-12850): ECDN Fallback Option Upon Inaccessible API Gateway

[lianbenjamin]

Description of the Changes

add support for ECDN fallback upon inaccessible API gateway:

• make a ping request of the configured cdn to check if accessible
• the ping request should be executed only when there is accessControlActions configured with a regexAction
• we should apply the regex replacement if a ping was made and it was successful, or regexAction exists and there is no timeout configured
• add new configuration provider.env.replaceHostOnlyManifestUrls with default false, which indicates whether only playManifest urls should be applied with the regex; when configured to true- only play manifest urls should be replaced. if configured to false- in addition to manifest urls, apply the regex action to poster and captions urls

solves FEC-12850

CheckLists

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• test are passing in local environment
• Travis tests are passing (or test results are not worse than on master branch :))
• Docs have been updated