firebase-ios-sdk

Move to `domainURIPrefix` for FIRDynamicLinkComponents (#2119)

* Revert "Revert premature api changes (#2097)"
The new API is optional and current API is fully supported.

This reverts commit 46cb564067c3cfb720cf2adc33366ce651c59e17.

* Update comments to reflect API changes.

* Mark the FDLURLComponents initializer return as nullable.

* Run Style.

* Allow for new initializer for FIRDynamicLinkComponents to have a nullable instancetype return.

* Update Changelog for v3.3.0

* Keep deprecated method initalization separate.

* Comments updates and other minor fixes.

* Consider domainURIPrefixes for exact matches with incoming short/long URLs.

* Add warning for deprecated API if developer passes in a domain with a scheme.