Media: Change alt attribute field to textarea in media library.

Change the input field used for `alt` attributes in the media library views from a text input to a textarea. This gives users more flexibility in resizing the field for easier management of longer alt attributes. 

This patch includes a less-common use of `esc_attr` for a `textarea`. This is because the primary usage of the `alt` attribute will be escaped using `esc_attr`, and the value in editing should match the value output on the front end.

Props edent, sabernhardt, afercia, JavierCasares, audrasjb, joedolson.
Fixes #50066.

git-svn-id: https://develop.svn.wordpress.org/trunk@54243 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/css/media-views.css

@@ -100,6 +100,7 @@
 	color: #2c3338;
 	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
 	font-size: 13px;
+	line-height: 1.38461538;
 }
 
 .media-frame input[type="text"],
@@ -529,6 +530,13 @@
 	resize: vertical;
 }
 
+.media-sidebar .alt-text textarea,
+.attachment-details .alt-text textarea,
+.compat-item .alt-text textarea,
+.alt-text textarea {
+	height: 50px;
+}
+
 .compat-item {
 	float: left;
 	width: 100%;
@@ -2798,6 +2806,7 @@
 	.media-frame textarea,
 	.media-frame select {
 		font-size: 16px;
+		line-height: 1.5;
 	}
 
 	.media-frame .media-toolbar input[type="search"] {