MM-27936: Allow resizing the channel sidebar and right-hand sidebar (#23117)

* MM-27936: Resize sidebar

* separate sidebar related constants into different file

* reset style when sidebar expanded

* change not to save user_id when saving to local_storage

* prevent a separation between the rhs and the main center panel

* change variable name

* migrate to css-based paradigm

* delete unnecessary files

* update snapshot

* increase the resizable range

* fix transition

* Made RHS and LHS widths not be saved scoped by team

* scope cleanup

* fix lhs header menu ellipsis/tolerances

* fix lint

* remove a ref from a dependency

* return null instead of empty jsx

* return null when disabled

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: harshil Sharma <harshilsharma63@gmail.com>
Co-authored-by: Caleb Roseland <caleb@calebroseland.com>

webapp/channels/src/selectors/lhs.ts

@@ -9,11 +9,16 @@ import {makeGetDraftsCount} from 'selectors/drafts';
 import {
     isCollapsedThreadsEnabled,
 } from 'mattermost-redux/selectors/entities/preferences';
+import {SidebarSize} from 'components/resizable_sidebar/constants';
 
 export function getIsLhsOpen(state: GlobalState): boolean {
     return state.views.lhs.isOpen;
 }
 
+export function getLhsSize(state: GlobalState): SidebarSize {
+    return state.views.lhs.size;
+}
+
 export function getCurrentStaticPageId(state: GlobalState): string {
     return state.views.lhs.currentStaticPageId;
 }

webapp/channels/src/selectors/rhs.ts

@@ -13,11 +13,16 @@ import {localizeMessage} from 'utils/utils';
 import {GlobalState} from 'types/store';
 import {RhsState, FakePost, SearchType} from 'types/store/rhs';
 import {PostDraft} from 'types/store/draft';
+import {SidebarSize} from 'components/resizable_sidebar/constants';
 
 export function getSelectedPostId(state: GlobalState): Post['id'] {
     return state.views.rhs.selectedPostId;
 }
 
+export function getRhsSize(state: GlobalState): SidebarSize {
+    return state.views.rhs.size;
+}
+
 export function getSelectedPostFocussedAt(state: GlobalState): number {
     return state.views.rhs.selectedPostFocussedAt;
 }