Rename "array of type si64" to "tensor constant of type si64" (#314)
Rename "array of type si64" to "tensor constant of type si64" (#314)

I remembered that in the spec we already define "tensor constant", so
let's use that definition.
openxla/stablehlo,openxla/stablehlo,openxla/stablehlo,openxla/stablehlo