Fix object_id method

[st0012]

In the past, even if you call object_id on the exact same object, it returns different values every time. This PR is to fix that issue + some refactoring around object initialization functions.

[codecov[bot]]

Codecov Report

Merging #796 into master will increase coverage by 0.02%. The diff coverage is 87.87%.

@@            Coverage Diff             @@
##           master     #796      +/-   ##
==========================================
+ Coverage   80.22%   80.24%   +0.02%     
==========================================
  Files          54       54              
  Lines        7399     7402       +3     
==========================================
+ Hits         5936     5940       +4     
+ Misses       1238     1237       -1     
  Partials      225      225

Impacted Files	Coverage Δ
vm/decimal.go	94.64% <100%> (ø)	:arrow_up:
vm/match_data.go	64.51% <100%> (ø)	:arrow_up:
vm/error.go	70.96% <100%> (ø)	:arrow_up:
vm/go_map.go	82.45% <100%> (ø)	:arrow_up:
vm/float.go	80.91% <100%> (ø)	:arrow_up:
vm/null.go	87.5% <100%> (ø)	:arrow_up:
vm/integer.go	64.37% <100%> (ø)	:arrow_up:
vm/boolean.go	93.33% <100%> (ø)	:arrow_up:
vm/range.go	93.29% <100%> (ø)	:arrow_up:
vm/regexp.go	75.51% <100%> (ø)	:arrow_up:
... and 14 more

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[st0012]

@saveriomiroddi ah you're right, my bad 😕

[st0012]

@saveriomiroddi updated, will merge after build finished