Replace manual string lexing

We currently have an ugly hack that manually lexes strings instead of utilizing Alex syntax: https://gitlab.haskell.org/ghc/ghc/-/blob/610840eb5bf6bd59417b82cc61e74aeaacbe5462/compiler/GHC/Parser/Lexer.x?page=3#L2184

The comment here suggests that it might duplicate work between the regex and the assembly of the token: https://gitlab.haskell.org/ghc/ghc/-/blob/610840eb5bf6bd59417b82cc61e74aeaacbe5462/compiler/GHC/Parser/Lexer.x?page=3#L663-666

But after some prototyping, it seems to work out rather nicely. Some advantages of avoiding our manual lexing:

1. The lexer more closely follows the spec in the Haskell Report
2. The logic is simplified, with the custom logic only needing to postprocess the character stream, and not worry about lexical errors
3. It seems to reduce memory usage

added needs triage label

mentioned in merge request !13128 (closed)

changed the description

removed needs triage label

added Pnormal compiler perf parser labels

assigned to @brandonchinn178

mentioned in commit 7378f606

mentioned in commit 05589606

mentioned in commit b7f2b438

mentioned in commit e7c83fe4

mentioned in commit 36846fdf

mentioned in commit c3c4e738

mentioned in commit 944d47ce

mentioned in commit c1b8b91a

mentioned in commit 61cc4c1d

mentioned in commit 40878c2d

mentioned in commit 92f9a4df

mentioned in commit de860cdc

mentioned in commit bb030d0d

closed