Keep the location of templates without interpolations through ast0
Why
On the v0 wire, a template without interpolations was one string constant at its segment's location, which ends before the closing backquote, so the template lost one character of its location after a PPX round trip. The constant now takes the template's location, and the segment's location is derived from it on the way back (#9164).
modifiedAST template after the v0 round trip
let z = `template`text
Before
After
parsed: expression [1,0+8]..[1,0+18]parsed: expression [1,0+8]..[1,0+18]after the round trip: expression [1,0+8]..[1,0+17]after the round trip: expression [1,0+8]..[1,0+18]