Olivero header-search-wide.pcss.css and header-search-narrow.pcss.css adjustments

Problem/Motivation

These changes are coming from the feedback that we've received from the patch submission that we've made on 9/23/2020.

1. +++ b/core/themes/olivero/css/components/header-search-narrow.pcss.css
   @@ -0,0 +1,174 @@
   +  form {
   

   We could make this element of the .search-block.

2. +++ b/core/themes/olivero/css/components/header-search-wide.pcss.css
   @@ -0,0 +1,292 @@
   +.search-wide__wrapper {
   

   This could be just .block-search--wide.

3. +++ b/core/themes/olivero/css/components/header-search-wide.pcss.css
   @@ -0,0 +1,292 @@
   +.search-wide__grid {
   

   This should probably also be an element of .block-search.

4. +++ b/core/themes/olivero/css/components/header-search-wide.pcss.css
   @@ -0,0 +1,292 @@
   +    .icon--search {
   

   This should be an element of .block-search.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes