stg-spec: Modify file paths according to new module hierarchy
This patch updates file paths according to new module hierarchy [1]:
- GHC/Stg/Syntax.hs <= stgSyn/StgSyn.hs
- GHC/Types/Literal.hs <= basicTypes/Literal.hs
- GHC/Types/CostCentre.hs <= profiling/CostCentre.hs
This patch also updates old file path [2]:
- utils/genapply/Main.hs <= utils/genapply/GenApply.hs
[1] https://gitlab.haskell.org/ghc/ghc/-/wikis/Make-GHC-codebase-more-modular
[2] commit 0cc4aad3
[skip ci]