[Search] Search frontend plugin (#3086)

* feat(search) search plugin

* feat(search): search page components

* feat(search): api

* feat(search): filters wip

* feat(search): wip filters

* fix(search): delete unused useParams hook

* fix(search): update docs

* fix(search): use latest versions of dependencies

* fix(search): change version of catalog plugin

* fix(search api): pass instance of catalog api to search api

* fix(filters): rename component from FilterButton to FiltersButton

* fixup

* fix(filters): use list of checkboxes to match style of catalog page filters

* fix(styles): use theme spacing for margins and paddings, delete unused styles

* fix(search): change terminology of search input to be more consistent and clear

* fix(search): restructure component exports according to ADR

* fix(search): replace sm with xs on Grid components to support smaller screens

* fix(search): add types

* fixup

* fix(search): bump backstage core

* change versions of backstage theme and dev-utils

.github/CODEOWNERS

@@ -9,5 +9,6 @@
 /plugins/cost-insights                      @backstage/silver-lining
 /plugins/cloudbuild                         @trivago/ebarrios
 /plugins/techdocs                           @backstage/techdocs-core
+/plugins/search                             @backstage/techdocs-core
 /plugins/techdocs-backend                   @backstage/techdocs-core
 /.changeset/cost-insights-*                 @backstage/silver-lining