Dynflags refactoring V (#17957)

More work towards avoiding DynFlags use (cf #17957). Commit messages:

1. CmmToAsm DynFlags refactoring

   • Remove DynFlags parameter from isDynLinkName: isDynLinkName used to test the global ExternalDynamicRefs flag. Now we test it outside of isDynLinkName

   • Add new fields into NCGConfig: current unit id, sse/bmi versions, externalDynamicRefs, etc.

   • Replace many uses of DynFlags by NCGConfig

   • Moved BMI/SSE datatypes into GHC.Platform

2. Avoid sdocWithDynFlags in pprCLbl

   • add a DynFlags parameter to pprCLbl
   • put maybe_underscore and pprAsmCLbl in a where clause to avoid DynFlags parameters

3. Avoid using sdocWithDynFlags

   Remove one use of sdocWithDynFlags from GHC.CmmToLlvm.llvmCodeGen' and from GHC.Driver.CodeOutput.profilingInitCode

4. Avoid DynFlags in Ppr code

   • replace DynFlags parameters with SDocContext parameters for a few Ppr related functions: bufLeftRenderSDoc, printSDoc, printSDocLn, showSDocOneLine.

   • remove the use of pprCols :: DynFlags -> Int in Outputable. We already have the information via sdocLineLength :: SDocContext -> Int

5. GHC.Runtime: avoid DynFlags

   • add getPlatform :: TcM Platform helper
   • remove unused DynFlags parameter from emptyPLS

6. Use ParserFlags in GHC.Runtime.Eval

   Instead of passing DynFlags to functions such as isStmt and hasImport in GHC.Runtime.Eval we pass ParserFlags. It's a much simpler structure that can be created purely with mkParserFlags'.