fix: Layout of large font labels in IEEE 745 floating point tool (#1337)

### Problem description
The issue seems to only affect the web version of ImHex but it is not
clear why. The labels of the checkboxes that represent bits in the IEEE
745 floating point tool were lay out incorrectly.

### Implementation description
The new code ensures that the bit labels are centered and located in the
middle of the checkbox regardless of the font size and the dear imgui
sized checkboxes.

plugins/builtin/source/content/tools_entries.cpp

@@ -1397,13 +1397,12 @@ namespace hex::plugin::builtin {
 
             const static auto IndentBoxOrLabel = [](
                                 u32 startBit, u32 bitIndex, u32 count, bool isLabel) {
-                int columnWidth = ImGui::GetColumnWidth();
                 int checkBoxWidth;
-                std::string labelString = "xx";
-                checkBoxWidth = ImGui::CalcTextSize(labelString.c_str()).x + 1;
+                std::string labelString = "#";
+                checkBoxWidth = ImGui::CalcTextSize(labelString.c_str()).x + ImGui::GetStyle().FramePadding.x * 2.0f;
                 float result = checkBoxWidth * (startBit - bitIndex) + 1;
                 if (count < 4) {
-                    result += (columnWidth - count * checkBoxWidth + 1) / 2.0f;
+                    result += (ImGui::GetStyle().FramePadding.x  + 0.5f);
                 }
                 if (isLabel) {
                      labelString = fmt::format("{}", startBit);