Fix negative gas cost in debug_traceTransaction traces

[natebeauregard]

Fixes #6669, #6810

Changes

• Adds a check to ensure that the GasCost trace entry is not overwritten after the STOP or RETURN opcodes are executed and the gas cost is properly recorded in the trace entry
• This approach is based on the way that ParityLikeTxTracer handles this situation

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Description

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No