refactor: replace toUint64Le, parseEpoch from ckbCore.utils with lumos

[twhy]

No description provided.

[homura]

While refactoring, it is better to keep the ckbCore as it is to let the reviewer know that all the uint64-related encoding has been completed

declare const originalCkbCore;

export const ckbCore = {
  someMethod: originalCkbCore.someMethod.bind(originalCkbCore),
  // ...
  utils: {
    toUint64() {
      // return ...
    }
  }
}

[twhy]

While refactoring, it is better to keep the ckbCore as it is to let the reviewer know that all the uint64-related encoding has been completed

declare const originalCkbCore;

export const ckbCore = {
  someMethod: originalCkbCore.someMethod.bind(originalCkbCore),
  // ...
  utils: {
    toUint64() {
      // return ...
    }
  }
}

@homura After checking the code, I realized we probably don't need to add a proxy ckbCore to get this refactor done.

The ckbCore object is still there. This screenshot shows the changes more clearly.
And all uint64-related encoding has been completed in this PR.

[twhy]

@Keith-CY Let's merge this.