add source to monthly statement

[LaurenWags]

Description

If a transaction (such as AC) is split between VG and Uphold funds, source should be shown on Monthly statement.

Example: #8828

Steps to Reproduce

1. Enable rewards
2. Claim grant (20 BAT)
3. Connect KYC uphold
4. Set AC to 50 BAT and add verified publishers to AC table
5. Wait for AC to be triggered
6. Look at Monthly Statement

Actual result:

two lines for AC, does not indicate source of each

Expected result:

we should add the source for each line

Reproduces how often:

easily

Brave version (brave://version info)

Brave	1.7.82 Chromium: 80.0.3987.162 (Official Build) dev (64-bit)
Revision	f2c5dd6138153bb0658091205bd1a1717f16081a-refs/branch-heads/3987@{#1034}
OS	macOS Version 10.14.6 (Build 18G3020)

Version/Channel Information:

• Can you reproduce this issue with the current release? n/a
• Can you reproduce this issue with the beta channel? yes
• Can you reproduce this issue with the dev channel? yes
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

cc @NejcZdovc @jenn-rhim @mandar-brave per our conversations

[GeetaSarvadnya]

Verification passed on

Brave	1.9.52 Chromium: 81.0.4044.129 (Official Build) dev (64-bit)
Revision	3d71af9f5704a40b85806f4d08925db24605ba25-refs/branch-heads/4044@{#979}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified the STR from the description
• Verified the test plan from brave/brave-core#5210
  
• Encountered #8938

Verification passed on

Brave	1.9.62 Chromium: 81.0.4044.138 (Official Build) dev (64-bit)
Revision	8c6c7ba89cc9453625af54f11fd83179e23450fa-refs/branch-heads/4044@{#999}
OS	Ubuntu 18.04 LTS

• Verified the STR from the description
• Verified the test plan from brave/brave-core#5210