EBS: Add disk_size param to calculate hourly usage & rate

[myersCody]

Add a disk_size param to the ebs generator and use it to calculate the cost & usage amount.

I used this yaml file:

```---
  generators:
    - EBSGenerator:
        start_date: 2023-11-01
        product_sku: VEAJHRNBBBBD
        resource_id: 12345674
        disk_size: 10
        rate: 0.1
        tags:
          resourceTags/user:storageclass: gamma
          resourceTags/user:Mapping: d1
          resourceTags/user:Map: d2
        cost_category:
          costCategory/env: ephemeral



  accounts:
    payer: 9999999999999
    user:
      - 9999999999999
    currency_code: USD #can be changed when testing with foreign currency codes```

To produce this CSV file with these changes

November-2023-None.csv

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.9%. Comparing base (92ec26b) to head (14a3664).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #526     +/-   ##
=======================================
+ Coverage   93.8%   93.9%   +0.1%     
=======================================
  Files         62      62             
  Lines       4719    4719             
  Branches     671     671             
=======================================
+ Hits        4426    4431      +5     
+ Misses       153     151      -2     
+ Partials     140     137      -3