PLT-5747: Fixed inconsistent on-hover, tooltip, and active states for buttons. (#7174)

* Fixed LHS Team Sidebar on hover highlight.
 * Fixed LHS Main Menu on hover tooltip to show "Main menu".
 * Added On-hover highlight for Favorite button in channel heading.
 * Added active state for channel members icon.
   * Added active class based on internal react state with new changeCss rule.
 * Changed cursor to pointer on hovering a theme.
 * Fixed Invite New Member Add Button to have text-underline on hover.

webapp/sass/components/_modal.scss

@@ -692,3 +692,9 @@
         padding-left: 0;
     }
 }
+
+.modal-invite-member {
+  .btn:hover {
+    text-decoration: underline;
+  }
+}

webapp/sass/layout/_headers.scss

@@ -157,12 +157,10 @@
 .channel-header__info {
     margin-top: 12px;
     white-space: nowrap;
-
+    .header-dropdown__icon {
+        color: $dark-gray;
+    }
     .channel-header__title {
-        .header-dropdown__icon {
-            color: $dark-gray;
-        }
-
         > a {
             display: inline-block;
             text-decoration: none;
@@ -458,7 +456,6 @@
     &.inactive {
         color: inherit;
 
-        &:hover,
         &:active {
             color: inherit;
         }

webapp/sass/layout/_team-sidebar.scss

@@ -25,6 +25,9 @@
                     display: block;
                     margin-left: 11px;
                     text-decoration: none;
+                    &:hover .team-btn {
+                      border-color: white;
+                    }
                 }
 
                 .team-btn {

webapp/sass/routes/_settings.scss

@@ -225,6 +225,9 @@
 
                         img {
                             border: 3px solid transparent;
+                            &:hover {
+                              cursor: pointer;
+                            }
                         }
 
                         .active {