Use blockstream API for native segwit address balance queries

[LefterisJP]

Fix #1639

[codecov]

Codecov Report

Merging #1647 into develop will decrease coverage by 0.10%.
The diff coverage is 50.00%.

@@             Coverage Diff             @@
##           develop    #1647      +/-   ##
===========================================
- Coverage    70.18%   70.07%   -0.11%     
===========================================
  Files          376      376              
  Lines        20778    20765      -13     
  Branches      3073     3067       -6     
===========================================
- Hits         14582    14551      -31     
- Misses        5426     5440      +14     
- Partials       770      774       +4     

Flag	Coverage Δ
#backend	80.52% <50.00%> (-0.14%)	⬇️
#frontend_integration	48.78% <ø> (-0.03%)	⬇️
#frontend_unit	21.38% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
rotkehlchen/chain/bitcoin/xpub.py	65.45% <ø> (ø)
rotkehlchen/chain/manager.py	85.35% <ø> (+1.14%)	⬆️
rotkehlchen/externalapis/etherscan.py	75.80% <0.00%> (-1.92%)	⬇️
rotkehlchen/chain/bitcoin/__init__.py	66.66% <48.00%> (ø)
rotkehlchen/utils/misc.py	86.11% <100.00%> (-0.56%)	⬇️
rotkehlchen/chain/ethereum/manager.py	86.02% <0.00%> (-4.35%)	⬇️
rotkehlchen/chain/ethereum/makerdao/dsr.py	53.41% <0.00%> (-2.49%)	⬇️
rotkehlchen/premium/sync.py	80.00% <0.00%> (-0.67%)	⬇️
rotkehlchen/premium/premium.py	70.39% <0.00%> (-0.66%)	⬇️
... and 7 more

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[LefterisJP]

Merging this. The only error is on Github actions and it's a timeout on yearn vaults test. Perhaps should increase timeout limits on that test.