Copy jsdoc from goog.Thenable onto goog.Promise. RELNOTES: n/a
Copy jsdoc from goog.Thenable onto goog.Promise.
RELNOTES: n/a

PiperOrigin-RevId: 377996199
Change-Id: I5aff4de550494041743146d63b8e41a4dd296f4b

google/closure-library,google/closure-library,google/closure-library,google/closure-library,google/closure-library