kaia: change package name of interfaces.go

[yoomee1313]

Proposed changes

• This PR changes the package name of interfaces.go.( klaytn -> kaia)
• It is an interface for kaia, so name should be kaia.

• It will be referenced as below.

  
  import (
      ...
  "github.com/kaiachain/kaia"
      ...
  )
  
  callMsg := kaia.CallMsg{ ... }

## Types of changes

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- [ ] Bugfix
- [ ] New feature or enhancement
- [ ] Others

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## Related issues

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## Further comments

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[blukat29]

Thanks @yoomee1313. Please replace kaia "github.com/kaiachain/kaia" with "github.com/kaiachain/kaia" as well.

[yoomee1313]

Hi @blukat29, Updated the code not to rename package kaia.