Add setting to hide avatars of rooms you have been invited to. (#29497)

* Add ability to block images of rooms you have been invited to.

* strings

* Add tests

* fix snapshot

* tweaks

* lint

test/unit-tests/components/views/avatars/__snapshots__/RoomAvatar-test.tsx.snap

@@ -1,5 +1,44 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`RoomAvatar should not render an invite avatar if the user has disabled it 1`] = `
+<div>
+  <span
+    class="_avatar_1qbcf_8 mx_BaseAvatar _avatar-imageless_1qbcf_52"
+    data-color="6"
+    data-testid="avatar-img"
+    data-type="round"
+    role="presentation"
+    style="--cpd-avatar-size: 36px;"
+  >
+    t
+  </span>
+</div>
+`;
+
+exports[`RoomAvatar should render an avatar for a room the user is invited to 1`] = `
+<div>
+  <span
+    aria-label="Avatar"
+    class="_avatar_1qbcf_8 mx_BaseAvatar"
+    data-color="6"
+    data-testid="avatar-img"
+    data-type="round"
+    style="--cpd-avatar-size: 36px;"
+  >
+    <img
+      alt=""
+      class="_image_1qbcf_41"
+      data-type="round"
+      height="36px"
+      loading="lazy"
+      referrerpolicy="no-referrer"
+      src="http://this.is.a.url/example.com/foobar"
+      width="36px"
+    />
+  </span>
+</div>
+`;
+
 exports[`RoomAvatar should render as expected for a DM room 1`] = `
 <div>
   <span