migrate to std::ranges

Move the various seq_ functions, as well as std::(stable_)sort,
std::accumulate, std::transform, std::find, std::find_if to their C++20
std::ranges counterparts.

mu/mu-cmd-extract.cc

@@ -63,7 +63,7 @@ save_parts(const Message& message, const std::string& filename_rx,
 			else if (opts.extract.save_attachments &&
 			    part.looks_like_attachment())
 				return true;
-			else if (seq_some(opts.extract.parts,
+			else if (std::ranges::any_of(opts.extract.parts,
 				     [&](auto&& num){return num==partnum;}))
 				return true;
 			else if (!filename_rx.empty() && part.raw_filename()) {

mu/mu-cmd-info.cc

@@ -144,10 +144,10 @@ topic_combi_fields(const Options& opts)
 	Table fields;
 	fields.add_row({"combi-field", "fields"});
 
-	seq_for_each(combi_fields(), [&](const auto& cfield) {
+	std::ranges::for_each(combi_fields(), [&](const auto& cfield) {
 
 		std::string fnames;
-		seq_for_each(cfield.fields, [&](auto&& field) {
+		std::ranges::for_each(cfield.fields, [&](auto&& field) {
 			if (!fnames.empty())
 				fnames += ", ";
 			fnames +=  mu_format("{}", field.name);

mu/mu-cmd-move.cc

@@ -49,7 +49,7 @@ Mu::mu_cmd_move(Mu::Store& store, const Options& opts)
 			   "Must have at least one of destination and flags");
 	else if (!dest.empty()) {
 		const auto mdirs{store.maildirs()};
-		if (!seq_some(mdirs, [&](auto &&d){ return d == dest;}))
+		if (!std::ranges::any_of(mdirs, [&](auto &&d){ return d == dest;}))
 			return Err(Error{Error::Code::InvalidArgument,
 					"No maildir '{}' in store", dest}
 				.add_hint("Try 'mu mkdir'"));

mu/mu-cmd-script.cc

@@ -30,7 +30,7 @@ Mu::mu_cmd_script(const Options& opts)
 {
 	ScriptPaths paths = { MU_SCRIPTS_DIR };
 	const auto&& scriptinfos{script_infos(paths)};
-	auto script_it = Mu::seq_find_if(scriptinfos, [&](auto&& item) {
+	auto script_it = std::ranges::find_if(scriptinfos, [&](auto&& item) {
 		return item.name == opts.script.name;
 	});
 

mu/mu-cmd-view.cc

@@ -46,7 +46,7 @@ static std::string /* return comma-sep'd list of attachments */
 get_attach_str(const Message& message, const Options& opts)
 {
 	std::string str;
-	seq_for_each(message.parts(), [&](auto&& part) {
+	std::ranges::for_each(message.parts(), [&](auto&& part) {
 		if (auto fname = part.raw_filename(); fname) {
 			if (str.empty())
 				str = fname.value();