Make border methods always require an explicit width (#11450)

This PR makes the `border` methods require an explicit width instead of
defaulting to 1px.

This breaks convention with Tailwind, but it makes GPUI more consistent
with itself. We already have an edge case where the parameterized method
had to be named `border_width`, since `border` was taken up by an alias
for the 1px variant.

### Before

```rs
div()
    .border()
    .border_t()
    .border_r()
    .border_b()
    .border_l()
    .border_width(px(7.))
```

### After

```rs
div()
    .border_1()
    .border_t_1()
    .border_r_1()
    .border_b_1()
    .border_l_1()
    .border(px(7.))
```

Release Notes:

- N/A

crates/gpui_macros/src/style_helpers.rs

@@ -86,12 +86,7 @@ fn generate_methods() -> Vec<TokenStream2> {
 
     for (prefix, fields, prefix_doc_string) in border_prefixes() {
         methods.push(generate_custom_value_setter(
-            // The plain method names (e.g., `border`, `border_t`, `border_r`, etc.) are special-cased
-            // versions of the 1px variants. This better matches Tailwind, but breaks our existing
-            // convention of the suffix-less variant of the method being the one that accepts a custom value
-            //
-            // To work around this, we're assigning a `_width` suffix here.
-            &format!("{prefix}_width"),
+            prefix,
             quote! { AbsoluteLength },
             &fields,
             prefix_doc_string,
@@ -553,7 +548,6 @@ fn border_prefixes() -> Vec<(&'static str, Vec<TokenStream2>, &'static str)> {
 
 fn border_suffixes() -> Vec<(&'static str, TokenStream2, &'static str)> {
     vec![
-        ("", quote! { px(1.)}, "1px"),
         ("0", quote! { px(0.)}, "0px"),
         ("1", quote! { px(1.) }, "1px"),
         ("2", quote! { px(2.) }, "2px"),