fire tab switcher / manager sources pixel

[brindy]

Task/Issue URL: https://app.asana.com/0/392891325557410/1208882840835128/f
Tech Design URL:
CC:

Description:
Fires a pixel depending on what is going on when the user opens the tab switcher.

Also renames a couple of pixels for clarity.

Steps to test this PR:

1. Open the tab switcher from anywhere should fire m_tab_manager_opened_daily but only the first time during in a day
2. Open the tab switcher from anywhere should fire m_tab_manager_opened every time
3. Open the tab switcher on the new tab page should fire m_tab_manager_open_from_newtabpage every time
4. Open the tab switcher while on the serp should fire m_tab_manager_open_from_serp every time
5. Open the tab switcher while on a website should fire m_tab_manager_open_from_website every time

[Bunn]

Reviewed yesterday. Forgot to mark as done, my bad. LGTM