Rename `target_word_size` to `target_pointer_width`
Rename `target_word_size` to `target_pointer_width`

Closes #20421

[breaking-change]

achanda/rand,bluss/rand,GrahamDennis/rand,waynenilsen/rand,retep998/rand,ebfull/rand,huonw/rand,arthurprs/rand,bhickey/rand,shepmaster/rand