Rename factory functions from 'Create' to 'Make' (#3706)

Similar to #3705, we actually have a mix of `Make` and `Create` in
factory functions too, so this PR is normalizing on `Make`. It's
intended to be consistent with the naming choice for Carbon factory
functions.

Note, MakeSyntheticBlock is the only one I feel a little weird about
because llvm's own APIs use Create, and this is essentially wrapping
LLVM calls. But the flipside is it also feels like a vague line to draw,
when we also differ from LLVM coding style in other ways.

language_server/language_server.cpp

@@ -99,7 +99,7 @@ void LanguageServer::OnDocumentSymbol(
   vfs.addFile(file, /*mtime=*/0,
               llvm::MemoryBuffer::getMemBufferCopy(files_.at(file)));
 
-  auto buf = SourceBuffer::CreateFromFile(vfs, file, NullDiagnosticConsumer());
+  auto buf = SourceBuffer::MakeFromFile(vfs, file, NullDiagnosticConsumer());
   auto lexed = Lex::Lex(value_stores, *buf, NullDiagnosticConsumer());
   auto parsed = Parse::Parse(lexed, NullDiagnosticConsumer(), nullptr);
   std::vector<clang::clangd::DocumentSymbol> result;