Update Platform Controls (#13751)

Continuing from #13597, this PR refactors platform controls to extract a
generic set of platform controls that can be used for any platform that
does not define it's own/we don't use the system ones.

In the future, these controls will likely be used as a fallback on
windows as well when the windows icon font isn't available.

Release Notes:

- Added updated window controls on Linux

crates/ui/src/components/icon.rs

@@ -146,6 +146,10 @@ pub enum IconName {
     FontSize,
     FontWeight,
     Github,
+    GenericMinimize,
+    GenericMaximize,
+    GenericClose,
+    GenericRestore,
     Hash,
     HistoryRerun,
     Indicator,
@@ -290,6 +294,10 @@ impl IconName {
             IconName::FontSize => "icons/font_size.svg",
             IconName::FontWeight => "icons/font_weight.svg",
             IconName::Github => "icons/github.svg",
+            IconName::GenericMinimize => "icons/generic_minimize.svg",
+            IconName::GenericMaximize => "icons/generic_maximize.svg",
+            IconName::GenericClose => "icons/generic_close.svg",
+            IconName::GenericRestore => "icons/generic_restore.svg",
             IconName::Hash => "icons/hash.svg",
             IconName::HistoryRerun => "icons/history_rerun.svg",
             IconName::Indicator => "icons/indicator.svg",

crates/ui/src/styles/color.rs

@@ -23,6 +23,7 @@ pub enum Color {
     Selected,
     Success,
     Warning,
+    Custom(Hsla),
 }
 
 impl Color {
@@ -46,6 +47,7 @@ impl Color {
             Color::Selected => cx.theme().colors().text_accent,
             Color::Success => cx.theme().status().success,
             Color::Warning => cx.theme().status().warning,
+            Color::Custom(color) => *color,
         }
     }
 }