K6 test improvement

[xin-hedera]

Description:

This PR improves some k6 test cases

• Add DEFAULT_ACCOUNT_ID_CRYPTO_ALLOWANCE and DEFAULT_SPENDER_ID_CRYPTO_ALLOWANCE for cryptoAllowance test cases
• Move web3 estimate and modification test json data default to code
• Add fallback default for json vu data loading

Related issue(s):

Fixes #11419

Notes for reviewer:

will create accounts and crypto allowances, then set the values for the new env var in a separate PR for deploy branch.

Checklist

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)

[lfdt-bot]

🎉 Snyk checks have passed. No issues have been found so far.

✅ security/snyk check is complete. No issues have been found. (View Details)

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for b06f49b1	✅ ∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (b06f49b)	Report Missing	Report Missing	Report Missing
Head commit (29be44b)	59355	36152	60.91%

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#11505)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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Footnotes

1. Codacy didn't receive coverage data for the commit, or there was an error processing the received data. Check your integration for errors and validate that your coverage setup is correct. ↩

[steven-sheehy]

LGTM