Detail styling for account lists in reply dialog

* Use flex to lay out account lists
  * Stretch account entry to fill to end of row
  * Give account entry minimum width
  * Update margins and paddings accordingly

Change-Id: Id24f7cb67bb08816f9358098db8e538c4826052a

polygerrit-ui/app/elements/change/gr-account-entry/gr-account-entry.html

@@ -23,6 +23,7 @@ limitations under the License.
     <style>
       gr-autocomplete {
         display: inline-block;
+        flex: 1;
         overflow: hidden;
       }
     </style>

polygerrit-ui/app/elements/change/gr-account-list/gr-account-list.html

@@ -23,6 +23,12 @@ limitations under the License.
     <style>
       gr-account-chip {
         display: inline-block;
+        margin: 0 .2em .2em 0;
+      }
+      gr-account-entry {
+        display: flex;
+        flex: 1;
+        min-width: 10em;
       }
       .group {
         --account-label-suffix: ' (group)';

polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.html

@@ -58,6 +58,7 @@ limitations under the License.
       }
       .peopleList {
         display: flex;
+        padding-top: .1em;
       }
       .peopleListLabel {
         color: #666;
@@ -65,7 +66,9 @@ limitations under the License.
         padding-right: .5em;
       }
       gr-account-list {
+        display: flex;
         flex: 1;
+        flex-wrap: wrap;
       }
       #reviewerConfirmationOverlay {
         padding: 1em;

polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.html

@@ -22,6 +22,7 @@ limitations under the License.
     <style>
       input {
         font-size: 1em;
+        width: 100%;
       }
       input.borderless,
       input.borderless:focus {