Add sync promo to "bookmark added" dialog

[CDRussell]

Task/Issue URL: https://app.asana.com/1/137249556945/task/1211704631712055

Description

Adds a way for users adding a bookmark to see that they can sync bookmarks. Only shows if:

• user does not have sync set up already
• user has never dismissed it before
• feature flag is enabled for both syncPromotion.bookmarkAddedDialog and syncPromotion

Steps to test this PR

Sync disabled

• Fresh install on internal build type
• Visit a site, and use overflow to Add Bookmark
• Confirm the dialog contains the option to jump to sync
• Let the dialog auto-dismiss (after ~3.5s)
• Use overflow to Edit Bookmark and then delete it. Return to browser.
• Add bookmark again; confirm again the promo line is still shown and this time tap on it; verify it takes you to Sync & Backup

Sync already enabled

• Set up sync
• Visit a site, and use overflow to Add Bookmark
• Verify the sync promo is NOT shown

Feature disabled

• Fresh install
• Use feature flag inventory to disable syncPromotion.bookmarkAddedDialog
• Visit a site, and use overflow to Add Bookmark
• Verify the sync promo is NOT shown

Permanently dismiss

• Fresh install
• Visit a site, and use overflow to Add Bookmark
• Tap on the promo's overflow and choose to Hide
• Verify it disappears
• Bring up the dialog again and verify it doesn't reappear

[CDRussell]

• Add sync promo to "bookmark added" dialog #7136 👈 (View in Graphite)
• Move strings to correct module for bookmark added dialog #7127
• Make "bookmark added" dialog specific to that use case #7099 : 2 other dependent PRs (#7100 , #7124 )
• develop

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