refactor: combine date-suffixed rewards table into one table

[seanmcgary]

Description

Refactoring date-suffixed rewards table names into one combined table. For example,

gold_10_avs_od_reward_amounts_2025_01_27
                                           --------> rewards_gold_10_avs_od_reward_amounts
gold_10_avs_od_reward_amounts_2025_01_28
                                        

This PR also removes rewards_staging table, as it became redundant with the rewards_final.

Type of change

• Refactor (non-breaking change which does not add or remove functionality)

How Has This Been Tested?

1. ran this code on the full snapshot and let it run until the new rewards was generated.
2. ran this code on the slim snapshot and run rewards from 2024 and then from 2025.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• 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
• I have checked my code and corrected any misspellings