Revert "[clang-repl] Extend the C support. (#89804)"

This reverts commit 253c28fa.

This commit is causing failures on the lldb CI bots, e.g.
https://ci.swift.org/view/all/job/llvm.org/view/LLDB/job/as-lldb-cmake/4307/

On my local macOS desktop build,
```
bin/lldb-dotest -p TestImportBuiltinFileID.py
Assertion failed: (D->getLexicalDeclContext() == this && "Decl inserted into wrong lexical context"), function addHiddenDecl, file DeclBase.cpp, line 1692.

6  libsystem_c.dylib        0x0000000185f0b8d0 abort + 128
7  libsystem_c.dylib        0x0000000185f0abc8 err + 0
8  liblldb.19.0.0git.dylib  0x00000001311e5800 clang::DeclContext::addHiddenDecl(clang::Decl*) + 120
9  liblldb.19.0.0git.dylib  0x00000001311e5978 clang::DeclContext::addDecl(clang::Decl*) + 32
10 liblldb.19.0.0git.dylib  0x000000012f617b48 clang::Sema::ActOnStartTopLevelStmtDecl(clang::Scope*) + 64
11 liblldb.19.0.0git.dylib  0x000000012eaf76c8 clang::Parser::ParseTopLevelStmtDecl() + 208
12 liblldb.19.0.0git.dylib  0x000000012ec051fc clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) + 3412
13 liblldb.19.0.0git.dylib  0x000000012ec03274 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, clang::Sema::ModuleImportState&) + 2020
14 liblldb.19.0.0git.dylib  0x000000012eaca860 clang::ParseAST(clang::Sema&, bool, bool) + 604
15 liblldb.19.0.0git.dylib  0x000000012e8554c0 clang::ASTFrontendAction::ExecuteAction() + 308
16 liblldb.19.0.0git.dylib  0x000000012e854c78 clang::FrontendAction::Execute() + 124
17 liblldb.19.0.0git.dylib  0x000000012e76dcfc clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 984
18 liblldb.19.0.0git.dylib  0x000000012e784500 compileModuleImpl(clang::CompilerInstance&, clang::SourceLocation, llvm::StringRef, clang::FrontendInputFile, llvm::StringRef, llvm::StringRef, llvm::function_ref<void (clang::CompilerInstance&)>, llvm::function_ref<void (clang::CompilerInstance&)>)::$_1::operator()() const + 52
```
Reverting until Vassil has a chance to look int oit.