fix: ensure hex values are prefixed or fail

[camsjams]

Closes #1148

Storage slot json files do not prefix hex values:

[
  {
    "key": "f383b0ce51358be57daa3b725fe44acdb2d880604e367199080b4379c41bb6ed",
    "value": "0000000000000000000000000000000000000000000000000000000000000000"
  }
]

There is an issue worth pursuing separately, but I think its fine as is since storage-slots are presumed to be generated by forc and can therefore be trusted as a hex value.

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟢	Statements	86.42% (+0.02% 🔼)	5798/6709
🟡	Branches	70.14% (+0.03% 🔼)	862/1229
🟡	Functions	77.15%	959/1243
🟢	Lines	86.39% (+0.02% 🔼)	5550/6424

Show files with reduced coverage 🔻

St.❔	File	Statements	Branches	Functions	Lines
🟢	... / utils.ts	90.2% (-0.19% 🔻)	85.71% (+1.5% 🔼)	92.31%	89.13% (-0.23% 🔻)

Test suite run success

1394 tests passing in 249 suites.

Report generated by 🧪jest coverage report action from 71970d9

[danielbate]

Adding a testcase for the reduced coverage on utils.ts would be nice to have, but I will leave up to you 👍🏻