Goal: Fix source map mappings key and use relative line values

[algochoi]

Summary

This PR deprecates the previous mapping field and adds the mappings field to align itself closer to the sourcemap specs. In addition, it fixes the mappings so that it uses relative line values for the source line mapping.

Closes #4191 #4192

Test Plan

Added test to check the new field in the source map.

[michaeldiamant]

@algochoi Thanks for your efforts to address sourcemap spec deviations. ☕

[codecov]

Codecov Report

Merging #4198 (0914f80) into master (ae17d8e) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4198      +/-   ##
==========================================
+ Coverage   54.55%   54.59%   +0.03%     
==========================================
  Files         391      391              
  Lines       48788    48790       +2     
==========================================
+ Hits        26617    26636      +19     
+ Misses      19947    19935      -12     
+ Partials     2224     2219       -5     

Impacted Files	Coverage Δ
data/transactions/logic/sourcemap.go	100.00% <100.00%> (ø)
network/wsPeer.go	67.67% <0.00%> (-0.28%)	⬇️
ledger/acctupdates.go	69.56% <0.00%> (+0.13%)	⬆️
network/wsNetwork.go	64.89% <0.00%> (+0.19%)	⬆️
crypto/merkletrie/node.go	93.48% <0.00%> (+1.86%)	⬆️
crypto/merkletrie/trie.go	68.61% <0.00%> (+2.18%)	⬆️
ledger/tracker.go	76.62% <0.00%> (+3.46%)	⬆️

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