Add event logging to SRC-20 and SRC-7 standards

[bitzoic]

Type of change

• New feature

Description

At the moment, it's not possible for indexers to access token metadata like name, symbol, decimals, bridged Ethereum address, etc.

Logs have been added to both the SRC-20 standard and the SRC-7 metadata standard, emitted when these values are updated.

Changes

The following changes have been made:

• Adds the SetNameEvent event to the SRC-20 specification
• Adds the SetSymbolEvent event to the SRC-20 specification
• Adds the SetDecimalsEvent event to the SRC-20 specification
• Adds the TotalSupplyEvent event to the SRC-20 specification
• Adds the SetMetadataEvent event to the SRC-7 specification

Notes

• While SetNameEvent, SetSymbolEvent, and SetMetadataEvent use an Option for the updated value, the SetDecimalsEvent and TotalSupplyEvent do not
• Examples have been split into separate workspace projects to speed up CI and resolve issues with hitting GitHub internal limits

Related Issues

Closes #128

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.
• I have updated the changelog to reflect the changes on this PR.

[K1-R1]

The standard does not specify that the event MUST be emitted upon contract deployment, only when the metadata is updated in a function call. This means that for any metadata embedded into the contract as a configurable or constant, the event will never be emitted and picked up by the indexer

I think if we're adding these events to the standards then the standards should require embedded values be logged; I assume many assets will use embedded metadata that doesn't change and I don't think this would reliably solve the issue indexers are facing

[bitzoic]

The standard does not specify that the event MUST be emitted upon contract deployment, only when the metadata is updated in a function call. This means that for any metadata embedded into the contract as a configurable or constant, the event will never be emitted and picked up by the indexer

I think if we're adding these events to the standards then the standards should require embedded values be logged; I assume many assets will use embedded metadata that doesn't change and I don't think this would reliably solve the issue indexers are facing

The only issue I see here is the assumption that metadata is static. If metadata is algorithmically determined then a log would need to be emitted every block.