Check tx confirmation proofs

[sstone]

When a tx is confirmed. ask for and check a tx inclusion proof, and check the p.o.w of the block in which it was published as well as the following blocks.

[codecov-commenter]

Codecov Report

Merging #2373 (28dcda2) into master (fa985da) will decrease coverage by 0.02%. The diff coverage is 88.88%.

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@@            Coverage Diff             @@
##           master    #2373      +/-   ##
==========================================
- Coverage   85.71%   85.69%   -0.02%     
==========================================
  Files         214      214              
  Lines       17558    17579      +21     
  Branches      754      754              
==========================================
+ Hits        15050    15065      +15     
- Misses       2508     2514       +6     

Impacted Files	Coverage Δ
.../acinq/eclair/blockchain/bitcoind/ZmqWatcher.scala	86.46% <80.00%> (-0.84%)	:arrow_down:
...ir/blockchain/bitcoind/rpc/BitcoinCoreClient.scala	98.66% <100.00%> (+0.22%)	:arrow_up:

... and 4 files with indirect coverage changes