Remove Data field from serialized Transactions

[emlautarom1]

Partially addresses #5161

Changes

• Do not serialize the Data field, but use it as alias of Input when deserializing.

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

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

Notes on testing

• Test suite has been updated to reflect the changes
• Tested syncing Sepolia with Prysm v4.0.8

Documentation

Requires documentation update

• Yes
• No

Requires explanation in Release Notes

• Yes
• No

Remarks

While working on #5161 we found that the Data field is not part of the spec (https://ethereum.github.io/execution-apis/api-documentation/), so we removed it on #6036.

As documented on that PR, this could introduce issues with users that relied on this non-conformant field. During internal testing, we found that the Prysm CL relied on this so we rolled back the change on #6067.

After discussing it with the team, we decided to compromise in the following fashion: we will accept Data as an alias for Input when reading transactions from other applications, but we will not include such field when sending them.

[emlautarom1]

The "trick" used to support deserialization but ignore serialization is described here: https://stackoverflow.com/questions/43714050/multiple-jsonproperty-name-assigned-to-single-property/43715009#43715009

[smartprogrammer93]

I like this way of doing it

[LukaszRozmej]

Context: ethereum/go-ethereum#28077

[benaadams]

Would be good for me if this was merged sooner rather than later; as will be additional merge conflicts 😅