Exclude non-native assets from value_balance

[alexeykoren]

Exclude non-native assets from value_balance

[what-the-diff]

PR Summary

• Updated Documentation
  The instructions in the documentation have been clarified to specify "ZEC" when talking about the bundle value. This helps better understand the context and purpose of the bundle value.
• Added Filtering in Value Balance Calculation
  For calculating the value balance, we have added a new measure which only includes native assets. This modification helps in achieving more accuracy by taking into account only those assets which directly belong to the platform.

[PaulLaux]

Nice fix,
Approved with minor comments