Add promotions info to rewards internals page

[NejcZdovc]

We should add claimed promotions to internals page. We should also display how much BAT for each promotions is left.

[btlechowski]

Verification passed on

Brave	1.10.79 Chromium: 81.0.4044.138 (Official Build) dev (64-bit)
Revision	8c6c7ba89cc9453625af54f11fd83179e23450fa-refs/branch-heads/4044@{#999}
OS	Ubuntu 18.04 LTS

Verified test plan from the description
Verified Promotions section is present in brave://rewards-internals. Verified promotions are properly displayed

Verification passed on

Brave | 1.10.80 Chromium: 81.0.4044.138 (Official Build) dev (64-bit)
-- | --
Revision | 8c6c7ba89cc9453625af54f11fd83179e23450fa-refs/branch-heads/4044@{#999}
OS | Windows 10 OS Version 1803 (Build 17134.1006)

• Claimed UGP grants (Promotion1 and Promotion 2) and verified Rewards info is displayed as expected

• Performed AC and set recurring tips and sent on-time tips to verified pubs and ensured that the brave://rewards-internal page values updated accordingly.
• Verified wallet balance and the balance shown in rewards internal page is intact
  

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Verified passed with

Brave | 1.10.80 Chromium: 81.0.4044.138 (Official Build) dev (64-bit)
-- | --
Revision | 8c6c7ba89cc9453625af54f11fd83179e23450fa-refs/branch-heads/4044@{#999}
OS | macOS Version 10.14.6 (Build 18G3020)

• Confirmed Balance info and Promotions sections on brave://rewards-internals page:

• Confirmed Balance info sums as expected and shows breakdown of BAT as expected:

• Confirmed Promotions (UGP and Ad grants) only show claim info once they have been claimed in the UI:

• Confirmed tipping and AC cause expected BAT to decrease (Rewards BAT first since that is available)