[Android] Stats db operations in UI thread

[SergeyZhukovsky]

Description

We have warnings that do db operations in UI thread. We should move it out from there.
2020-08-13 12:06:17.883 29731-29731/com.brave.browser_default D/StrictMode: StrictMode policy violation; ~duration=169 ms: android.os.strictmode.DiskReadViolation
` at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:341)
at org.chromium.chrome.browser.local_database.DatabaseHelper.getTotalSavedBandwidthWithDate(DatabaseHelper.java:301)
at org.chromium.chrome.browser.brave_stats.BraveStatsBottomSheetDialogFragment.updateBraveStatsLayout(BraveStatsBottomSheetDialogFragment.java:155)
at org.chromium.chrome.browser.brave_stats.BraveStatsBottomSheetDialogFragment.onViewCreated(BraveStatsBottomSheetDialogFragment.java:151)

12:08
we read from stats sqlite db in`

Steps to reproduce

Actual result

Expected result

Issue reproduces how often

Version/Channel Information:

• Can you reproduce this issue with the current Play Store version?
• Can you reproduce this issue with the current Play Store Beta version?
• Can you reproduce this issue with the current Play Store Nightly version?

Device details

• Install type (ARM, x86):
• Device type (Phone, Tablet, Phablet):
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Brave version

Website problems only

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

Additional information