Convert all TopBottomPanel with Panel, and remove reference to TopBottomPanel when both SidePanel and TopBottomPanel were mentioned.

following those steps:
1. Rename `egui::TopBottomPanel` with `egui::Panel`.
2. Rename `height` with `size` in all chained methods.
    - `default_height()` to `default_size()`
    - `min_height()` to `min_size()`
    - `max_height()` to `max_size()`
    - `height_range()` to `size_range()`
    - `exact_height()` to `exact_size()`

if using `Panel::new()`, replace
- `TopBottomSide::Top` with `Side::Horizontal(HorizontalSide::Top)`
- `TopBottomSide::Bottom` with `Side::Horizontal(HorizontalSide::Bottom)`

NOTE: Non-working commit

crates/egui_demo_app/src/apps/http_app.rs

@@ -61,7 +61,7 @@ impl Default for HttpApp {
 
 impl eframe::App for HttpApp {
     fn update(&mut self, ctx: &egui::Context, frame: &mut eframe::Frame) {
-        egui::TopBottomPanel::bottom("http_bottom").show(ctx, |ui| {
+        egui::Panel::bottom("http_bottom").show(ctx, |ui| {
             let layout = egui::Layout::top_down(egui::Align::Center).with_main_justify(true);
             ui.allocate_ui_with_layout(ui.available_size(), layout, |ui| {
                 ui.add(egui_demo_lib::egui_github_link_file!())

crates/egui_demo_app/src/apps/image_viewer.rs

@@ -53,7 +53,7 @@ impl Default for ImageViewer {
 
 impl eframe::App for ImageViewer {
     fn update(&mut self, ctx: &egui::Context, _: &mut eframe::Frame) {
-        egui::TopBottomPanel::new(Side::Horizontal(HorizontalSide::Top), "url bar").show(
+        egui::Panel::new(Side::Horizontal(HorizontalSide::Top), "url bar").show(
             ctx,
             |ui| {
                 ui.horizontal_centered(|ui| {

crates/egui_demo_app/src/wrap_app.rs

@@ -296,7 +296,7 @@ impl eframe::App for WrapApp {
         }
 
         let mut cmd = Command::Nothing;
-        egui::TopBottomPanel::top("wrap_app_top_bar")
+        egui::Panel::top("wrap_app_top_bar")
             .frame(egui::Frame::new().inner_margin(4))
             .show(ctx, |ui| {
                 ui.horizontal_wrapped(|ui| {