Add Gas Limit Default

[sideninja]

Closes #373

Description

Gas limit is now required and CLI is fixed to pass default max value.

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For contributor use:

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov-commenter]

Codecov Report

Merging #374 (a1f3bb3) into master (5ea9616) will decrease coverage by 0.05%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #374      +/-   ##
==========================================
- Coverage   54.80%   54.74%   -0.06%     
==========================================
  Files          36       36              
  Lines        1872     1874       +2     
==========================================
  Hits         1026     1026              
- Misses        718      720       +2     
  Partials      128      128              

Flag	Coverage Δ
unittests	54.74% <0.00%> (-0.06%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/flowkit/transaction.go	0.00% <0.00%> (ø)

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