Fix block tree queries

[turuslan]

Referenced issues

Description of the Change

• Remove unused babe lottery and block tree code.
• Fix descending blocks query and test.
• Check forks earlier in hasDirectChain.
• Simplify and fix ascending blocks queries, because they are just descending blocks queries with reversed result.

Benefits

• Fixes wrong block requests near fork (kagome responded with wrong block).

Possible Drawbacks

Usage Examples or Tests

Alternate Designs

[codecov]

Codecov Report

Merging #1341 (42919c2) into master (31dd93a) will decrease coverage by 0.02%.
The diff coverage is 20.00%.

❗ Current head 42919c2 differs from pull request most recent head f791771. Consider uploading reports for the commit f791771 to get more accurate results

@@            Coverage Diff             @@
##           master    #1341      +/-   ##
==========================================
- Coverage   24.41%   24.38%   -0.03%     
==========================================
  Files         619      619              
  Lines       23079    23021      -58     
  Branches    12044    12011      -33     
==========================================
- Hits         5635     5614      -21     
+ Misses      12241    12225      -16     
+ Partials     5203     5182      -21     

Impacted Files	Coverage Δ
core/blockchain/block_tree.hpp	100.00% <ø> (ø)
core/blockchain/impl/block_tree_impl.hpp	33.33% <ø> (ø)
core/consensus/babe/babe_lottery.hpp	100.00% <ø> (ø)
core/consensus/babe/impl/babe_lottery_impl.cpp	28.57% <ø> (-5.33%)	⬇️
core/blockchain/impl/block_tree_impl.cpp	21.46% <20.00%> (-0.16%)	⬇️
core/blockchain/impl/cached_tree.cpp	54.00% <0.00%> (-2.00%)	⬇️

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