Change name of service container AddPipeline extensions

[daveaglick]

Some of the AddPipeline extensions register the pipeline class with the DI container which can be confusing ordering-wise. They should be renamed to RegisterPipeline or similar with appropriate code documentation explaining the difference. But because we don't want to outright break anyone given how common these methods are, the old ones shouldn't be removed but marked with ObsoleteAttribute and forward to the new ones instead.