compiler: remove unused GHC.Linker.Loader.loadExpr

This patch removes the unused `GHC.Linker.Loader.loadExpr` function.
It was moved from `GHC.Runtime.Linker.linkExpr` in `ghc-9.0` to
`GHC.Linker.Loader.loadExpr` in `ghc-9.2`, and remain completely
unused and untested ever since. There's also no third party user of
this function to my best knowledge, so let's remove this. Anyone who
wants to write their own GHC API function to load bytecode can consult
the source code in older release branches.

compiler/GHC/Linker/Loader.hs

@@ -17,7 +17,6 @@ module GHC.Linker.Loader
    , showLoaderState
    , getLoaderState
    -- * Load & Unload
-   , loadExpr
    , loadDecls
    , loadPackages
    , loadModule
@@ -589,52 +588,6 @@ preloadLib interp hsc_env lib_paths framework_paths pls lib_spec = do
           , "Try using a dynamic library instead."
           ]
 
-
-{- **********************************************************************
-
-                        Link a byte-code expression
-
-  ********************************************************************* -}
-
--- | Load a single expression, /including/ first loading packages and
--- modules that this expression depends on.
---
--- Raises an IO exception ('ProgramError') if it can't find a compiled
--- version of the dependents to load.
---
-loadExpr :: Interp -> HscEnv -> SrcSpan -> UnlinkedBCO -> IO ForeignHValue
-loadExpr interp hsc_env span root_ul_bco = do
-  -- Initialise the linker (if it's not been done already)
-  initLoaderState interp hsc_env
-
-  -- Take lock for the actual work.
-  modifyLoaderState interp $ \pls0 -> do
-    -- Load the packages and modules required
-    (pls, ok, _, _) <- loadDependencies interp hsc_env pls0 span needed_mods
-    if failed ok
-      then throwGhcExceptionIO (ProgramError "")
-      else do
-        -- Load the expression itself
-        -- Load the necessary packages and linkables
-        let le = linker_env pls
-            bco_ix = mkNameEnv [(unlinkedBCOName root_ul_bco, 0)]
-        resolved <- linkBCO interp (pkgs_loaded pls) le bco_ix root_ul_bco
-        [root_hvref] <- createBCOs interp [resolved]
-        fhv <- mkFinalizedHValue interp root_hvref
-        return (pls, fhv)
-  where
-     free_names = uniqDSetToList (bcoFreeNames root_ul_bco)
-
-     needed_mods :: [Module]
-     needed_mods = [ nameModule n | n <- free_names,
-                     isExternalName n,      -- Names from other modules
-                     not (isWiredInName n)  -- Exclude wired-in names
-                   ]                        -- (see note below)
-        -- Exclude wired-in names because we may not have read
-        -- their interface files, so getLinkDeps will fail
-        -- All wired-in names are in the base package, which we link
-        -- by default, so we can safely ignore them here.
-
 initLinkDepsOpts :: HscEnv -> LinkDepsOpts
 initLinkDepsOpts hsc_env = opts
   where