update gen-corpus to generate coin spends for solution-generator fuzzer

[arvidn]

the main feature is to generate corpus for the new solution-generator fuzzer, but also improves the generator to make other generators be disabled by default.

[coveralls-official]

Pull Request Test Coverage Report for Build 10973454748

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 92 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.6%) to 83.373%

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Files with Coverage Reduction	New Missed Lines	%
crates/chia-protocol/src/spend_bundle.rs	10	84.21%
crates/chia-protocol/src/block_record.rs	82	0.88%

Totals
Change from base Build 10948785887:	-0.6%
Covered Lines:	12275
Relevant Lines:	14723

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💛 - Coveralls