Deprecate alias & standardize parameter key definition of transform
Deprecate alias & standardize parameter key definition of transform

TFX users define each module in pipeline through different Key-value pairs.
1. The raw key string are used in different places. To avoid typo that may break the pipeline, define the key strings as public variables under types, and reuse the variables in other files.

2. The alias for each module is for upgrading the previous parameters into new ones. Since TFX has provided time for user migration, should remove the alias to keep codebase clean.

This diff is a cleanup on transform module.

PiperOrigin-RevId: 356832460

google/nitroml