Fix incorrect multiple-count report field sizing

- Add `HIDInputReportItem::get_total_size()`, the item's size times
its count
- Use `HIDInputReportItem::get_total_size()` to calculate the correct
item offset in `HIDInputReport::push_back`

Offsets for `HIDInputReportItem` instances within a report are
calculated using the size of the field, but the message will contain
N fields of the given size. As a result, multiple-count fields give
every following `HIDInputReportItem` an incorrect offset when parsing
HID reports. In addition, the report's calculated total size is
incorrect, which would cause issues with any code that might rely on its
size in the future.

Introducing a member to provide the correct total size allows correct
calculation of a report's size.

components/ble_client_hid/hid_parser.cpp

@@ -335,7 +335,7 @@ namespace esphome
     void HIDInputReport::push_back(HIDInputReportItem *item)
     {
       this->items.push_back(item);
-      this->report_size += item->report_size;
+      this->report_size += item->get_total_size();
     }
 
     std::vector<HIDReportItemValue> HIDReportMap::parse(uint8_t *hid_report_data)
@@ -370,6 +370,11 @@ namespace esphome
       return report_values;
     }
 
+    size_t HIDInputReportItem::get_total_size()
+    {
+      return this->report_size * this->report_count;
+    }
+
     int32_t HIDInputReportItem::parse_input_report_item(uint8_t *report_data, uint16_t bit_offset, uint16_t report_size, HIDLogicalRange logical_range)
     {
       int32_t value = 0;

components/ble_client_hid/hid_parser.h

@@ -91,6 +91,7 @@ namespace esphome
       {
         delete usage_collection;
       };
+      size_t get_total_size();
       virtual std::vector<HIDReportItemValue> parse(uint8_t *hid_report_data) = 0;
       static int32_t parse_input_report_item(uint8_t *report_data, uint16_t bit_offset, uint16_t report_size, HIDLogicalRange logical_range);
       const uint8_t report_size; // in bits