Use last opened panel when selecting sidepanel button in toolbar

[rebron]

Description

When selecting the side panel button, it will always open the reading list unless the user has removed the reading list from the sidebar, in which case the button will open the bookmarks panel.

Selecting the side panel button should use the last opened panel and toggle the last opened panel on open and close of that button.

Steps to Reproduce

1. Use 1.44.x and select the side panel button. (notice it opens reading list panel)
2. Select the bookmarks panel. And close side panel button
3. Open side panel button and notice it opens reading list panel. Expected to open bookmarks panel again.

Actual and Expected result:

see STR above.

Reproduces how often:

Easily.

Brave version (brave://version info)

1.44.x

Version/Channel Information:

• Can you reproduce this issue with the current release? n/a
• Can you reproduce this issue with the beta channel? yes
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Does the issue resolve itself when disabling Brave Rewards? n/a
• Is the issue reproducible on the latest version of Chrome? n/a

Miscellaneous Information:

[stephendonner]

Verified PASSED using

Brave	1.49.89 Chromium: 110.0.5481.77 (Official Build) beta (x86_64)
Revision	65ed616c6e8ee3fe0ad64fe83796c020644d42af-refs/branch-heads/5481@{#839}
OS	macOS Version 11.7.3 (Build 20G1116)

Steps:

1. installed 1.49.89
2. launched Brave
3. opened a new-tab page
4. clicked on the Show Sidebar button
5. confirmed it opened the Reading List in the left Sidebar panel
6. selected the Bookmarks icon in the Sidebar panel
7. clicked to close the Sidebar button
8. clicked again on the Show Sidebar button

Confirmed it opened with the Bookmarks panel

Step 5	Step 6	Step 7	result