system: some refactoring

There's no need to move a temporary which is already an rvalue

Clean-up some redundant attributes and function in settings.
Make sure C types are proxied to fixed-sized ones, not the other way around.

Clean-up webprint implementation
- use typed duration for the backlog
- don't duplicate members and types for config, just re-use the struct as-is
- don't go over-the-top with const members, just proxy through a method

code/espurna/web.cpp

@@ -64,17 +64,14 @@ namespace {
 #include "static/server.key.h"
 #endif // WEB_SSL_ENABLED
 
-AsyncWebPrint::AsyncWebPrint(const AsyncWebPrintConfig& config, AsyncWebServerRequest* request) :
-    mimeType(config.mimeType),
-    backlogCountMax(config.backlogCountMax),
-    backlogSizeMax(config.backlogSizeMax),
-    backlogTimeout(config.backlogTimeout),
+AsyncWebPrint::AsyncWebPrint(AsyncWebPrintConfig config, AsyncWebServerRequest* request) :
+    _config(config),
     _request(request),
     _state(State::None)
 {}
 
 bool AsyncWebPrint::_addBuffer() {
-    if ((_buffers.size() + 1) > backlogCountMax) {
+    if ((_buffers.size() + 1) > _config.backlog.count) {
         if (!_exhaustBuffers()) {
             _state = State::Error;
             return false;
@@ -83,7 +80,7 @@ bool AsyncWebPrint::_addBuffer() {
 
     // Note: c++17, emplace returns created object reference
     //       c++11, we need to use .back()
-    _buffers.emplace_back(backlogSizeMax, 0);
+    _buffers.emplace_back(_config.backlog.size, 0);
     _buffers.back().clear();
 
     return true;
@@ -103,7 +100,7 @@ bool AsyncWebPrint::_addBuffer() {
 void AsyncWebPrint::_prepareRequest() {
     _state = State::Sending;
 
-    auto *response = _request->beginChunkedResponse(mimeType, [this](uint8_t *buffer, size_t maxLen, size_t index) -> size_t {
+    auto *response = _request->beginChunkedResponse(_config.mimeType, [this](uint8_t *buffer, size_t maxLen, size_t index) -> size_t {
         switch (_state) {
         case State::None:
             return RESPONSE_TRY_AGAIN;
@@ -159,9 +156,13 @@ bool AsyncWebPrint::_exhaustBuffers() {
         _prepareRequest();
     }
 
-    const auto start = millis();
+    constexpr espurna::duration::Seconds Timeout { 5 };
+
+    using TimeSource = espurna::time::CoreClock;
+    const auto start = TimeSource::now();
+
     do {
-        if (millis() - start > 5000) {
+        if (TimeSource::now() - start > Timeout) {
             _buffers.clear();
             break;
         }
@@ -275,7 +276,6 @@ void _onGetConfig(AsyncWebServerRequest *request) {
     auto out = std::make_shared<String>();
     out->reserve(TCP_MSS);
 
-
     char buffer[256];
     int prefix_len = snprintf_P(buffer, sizeof(buffer),
             PSTR("{\n\"app\": \"%s\",\n\"version\": \"%s\",\n\"backup\": \"1\""),