Change update_moving_price() function

[shamil-gadelshin]

Description

We're changing update_moving_price() function to use FirstEmissionBlockNumber parameter instead of NetworkRegisteredAt. We need this change to take another block from the subnet lifecycle to calculate the moving price. Initially, we used the registration block, but the block of the invocation of start_call() function is more valid. start_call() sets FirstEmissionBlockNumber storage map and emits the related event.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run cargo fmt and cargo clippy to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Additional Notes

The new code expects start_call() to be called before update_moving_price(); otherwise, the first_emissions_block defaults to zero. The block affecting the calculation is FirstEmissionBlockNumber minus one block because start_block sets FirstEmissionBlockNumber to the next block instead of the current one.