fix(inputs): use base CSS param for border-radius (#3430)

There is a standard css variable --sapField_BorderCornerRadius meant to be used for Input's border radius. It is 0.125rem in sap_fiori_3 and sap_fiori_3_dark and 0 in all other themes. This allows changing the border radius of all inputs via the Theme Designer

Author: MarcusNotheis

packages/main/src/themes/Input.css

@@ -14,7 +14,7 @@
 	font-style: normal;
 	background-color: var(--sapField_Background);
 	border: 1px solid var(--sapField_BorderColor);
-	border-radius: var(--_ui5_input_wrapper_border_radius);
+	border-radius: var(--sapField_BorderCornerRadius);
 	box-sizing: border-box;
 	line-height: normal;
 	letter-spacing: normal;

packages/main/src/themes/ResponsivePopoverCommon.css

@@ -7,7 +7,7 @@
 	font-family: "72override", var(--sapFontFamily);
 	background-color: var(--sapField_Background);
 	border: 1px solid var(--sapField_BorderColor);
-	border-radius: var(--_ui5_input_wrapper_border_radius);
+	border-radius: var(--sapField_BorderCornerRadius);
 	box-sizing: border-box;
 }