PLT-6215 Major post list refactor (#6501)

* Major post list refactor

* Fix post and thread deletion

* Fix preferences not selecting correctly

* Fix military time displaying

* Fix UP key for editing posts

* Fix ESLint error

* Various fixes and updates per feedback

* Fix for permalink view

* Revert to old scrolling method and various fixes

* Add floating timestamp, new message indicator, scroll arrows

* Update post loading for focus mode and add visibility limit

* Fix pinning posts and a react warning

* Add loading UI updates from Asaad

* Fix refreshing loop

* Temporarily bump post visibility limit

* Update infinite scrolling

* Remove infinite scrolling

webapp/components/post_view/date_separator.jsx

@@ -0,0 +1,32 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import {FormattedDate} from 'react-intl';
+
+export default class DateSeparator extends React.PureComponent {
+    static propTypes = {
+
+        /*
+         * The date to display in the separator
+         */
+        date: PropTypes.instanceOf(Date)
+    }
+
+    render() {
+        return (
+            <div
+                className='date-separator'
+            >
+                <hr className='separator__hr'/>
+                <div className='separator__text'>
+                    <FormattedDate
+                        value={this.props.date}
+                        weekday='short'
+                        month='short'
+                        day='2-digit'
+                        year='numeric'
+                    />
+                </div>
+            </div>
+        );
+    }
+}