Replace @string/tab_tray_menu_item_save with @string/tab_tray_menu_select, Remove "Share all tabs" option from tab tray's private browsing menu

Co-authored-by: Johan Lorenzo <jlorenzo@mozilla.com>

Instead of simply fixing the memory leak for this issue by directly
removing references, it makes more sense to move the whole
BiometricPrompt out of the fragment and into it's own feature to be
re-usable.

While StrictMode is not exclusively used for performance purposes, it's
primarily used for perf purposes so let's move it to the perf package
and code owner it.

Our previous strategy was to code owner all the specific files we should
own but that's fragile and unreasonable. This is simpler. We expect
there will still be edge cases that live outside these directories (e.g.
*Application*kt).

Instead of listing many different files here, we should just put them in
/perf/ packages and code owner them.

I'm not convinced this is a useful test because the performance
characteristics seem unfortunately nuanced: if the test fails, it implies
you shouldn't add more but that isn't necessarily true (for example, if
your RV child has a large depth). Furthermore, we haven't measured in a
variety of circumstances that layouts like LinearLayout perform better
as RecyclerView children so maybe it only held for the one small case we
used it in.

set up preferences in onCreatePreferences instead of onResume so that their visibility is determined before the screen appears rather than after

comment link: https://github.com/mozilla-mobile/fenix/pull/16536#discussion_r522387945

updating share icon to a filled shape, like default toolbar menu across all app

replace mozac_ic_share for ic_hollow_share on DefaultToolbarMenu

* For #15761 - Part 1: Turn ON the showGridViewInTabsSettings feature flag

* For #15761 - Part 2: Remove the showGridViewInTabsSettings feature flag and show the Tab view preference category

Revert "For #15761 - [Grid View] Enable the grid view and remove its feature flag (#16535)" (#16544)

This reverts commit 7499d33b.

* Add top sites related strings

* Change default top sites to Baidu & JD in China build