Fix getTransactionReceiptsByBlock and TestGetTransactionReceiptsByBlock

[0xsharma]

We were facing the following issue:

• If a block has both normal and bor transactions, getTransactionReceiptsByBlock returns receipts where all the receipts have the same txn hash( = state-sync txHash )

In this PR, we solve the following :

• The getTransactionReceiptsByBlock bug.
• The testcase covering getTransactionReceiptsByBlock.

The link to the issue is here.

[codecov-commenter]

Codecov Report

Merging #477 (a69109c) into develop (7e79f82) will decrease coverage by 0.15%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           develop     #477      +/-   ##
===========================================
- Coverage    57.00%   56.84%   -0.16%     
===========================================
  Files          607      604       -3     
  Lines        69899    69877      -22     
===========================================
- Hits         39843    39720     -123     
- Misses       26665    26756      +91     
- Partials      3391     3401      +10     

Impacted Files	Coverage Δ
eth/backend.go	0.00% <0.00%> (ø)
node/defaults.go	24.13% <0.00%> (-6.90%)	⬇️
p2p/discover/v4_udp.go	72.75% <0.00%> (-5.51%)	⬇️
eth/downloader/fetchers.go	61.90% <0.00%> (-4.77%)	⬇️
accounts/keystore/watch.go	90.69% <0.00%> (-4.66%)	⬇️
p2p/enode/iter.go	88.34% <0.00%> (-2.92%)	⬇️
les/utils/exec_queue.go	88.88% <0.00%> (-2.78%)	⬇️
les/distributor.go	79.68% <0.00%> (-2.35%)	⬇️
les/servingqueue.go	56.97% <0.00%> (-2.33%)	⬇️
p2p/simulations/mocker.go	31.11% <0.00%> (-2.23%)	⬇️
... and 26 more

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