layout: Add very basic support for showing text in input boxes (#32365)

This only paints text in input fields. Selection and cursor are still
not painted.

In addition to adding this feature, the change also updates the
user-agent.css with the latest from the HTML specification. Extra
padding and extraneous settings (such as a bogus line-height and
min-height) are also removed from servo.css. This leads to some new
passes.

There are some new passes, this introduces failures as inserting text
reveals issues that were hidden before. Notably:

- failures in `/html/editing/editing-0/spelling-and-grammar-checking/`:
  We do not support spell-checking.
- Most of the rest of the new failures are missing features of input
  boxes that are also missing in legacy layout.

components/layout_2020/flow/construct.rs

@@ -191,6 +191,7 @@ where
     ) -> Self {
         let text_decoration_line =
             propagated_text_decoration_line | info.style.clone_text_decoration_line();
+
         BlockContainerBuilder {
             context,
             info,
@@ -214,6 +215,7 @@ where
             self.context,
             self.text_decoration_line,
             !self.have_already_seen_first_line_for_text_indent,
+            self.info.is_single_line_text_input(),
         ) {
             // There are two options here. This block was composed of both one or more inline formatting contexts
             // and child blocks OR this block was a single inline formatting context. In the latter case, we
@@ -598,6 +600,7 @@ where
             self.context,
             self.text_decoration_line,
             !self.have_already_seen_first_line_for_text_indent,
+            self.info.is_single_line_text_input(),
         ) {
             self.push_block_level_job_for_inline_formatting_context(inline_formatting_context);
         }