[signin] Add default avatar in the profile creation signin promo

Screenshot for light mode: https://drive.google.com/file/d/1cVocXW7_qV-OsW-RC5Q9_8oIc0UgAyZw/view?usp=sharing
Screenshot for dark mode: https://drive.google.com/file/d/1uG2qP8ZwzqPA1NHdvtt4rgpd9vX1aY-8/view?usp=sharing
The current image is temporary, it will be changed in a separate CL once
it will be ready.

Bug: 1105865
Change-Id: Ifea158663fa85147677c2ee0920c5a2aa2fa0bfc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2332660
Commit-Queue: Diana Zagidullina <dizg@google.com>
Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Monica Basta <msalama@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794947}

chrome/browser/resources/signin/profile_picker/profile_creation_flow/profile_type_choice.html

@@ -34,6 +34,19 @@
     width: 100%;
   }
 
+  #bannerContainer > img {
+    --avatar-size: 100px;
+    border: 2px solid var(--md-background-color);
+    border-radius: 50%;
+    bottom: calc(var(--avatar-size)/-2);
+    height: var(--avatar-size);
+    left: 0;
+    margin: auto;
+    position: absolute;
+    right: 0;
+    width: var(--avatar-size);
+  }
+
   #notNowButton {
     background: none;
     border: none;
@@ -65,6 +78,7 @@
         on-click="onTapBack_" aria-label="$i18n{backButtonLabel}">
     </cr-icon-button>
     <div id="banner"></div>
+    <img src="chrome://theme/IDR_PROFILE_AVATAR_PLACEHOLDER_LARGE">
 </div>
 <div class="title-container">
   <h2>$i18n{profileTypeChoiceTitle}</h2>