Addresses failures with the following, in some files:
-Wshorten-64-to-32
-Wimplicit-int-conversion
-Wsign-compare
-Wsign-conversion
-Wtautological-unsigned-zero-compare

(This specific CL focuses on .cc files in dirs n-t, except string.)

Bug: chromium:1292951
PiperOrigin-RevId: 465287204
Change-Id: I0fe98ff78bf3c08d86992019eb626755f8b6803e