[Desktop] Add Gemini widget to new tab page

[rebron]

Description

Add Gemini widget to the new tab page to allow for trading through Gemini.

Steps to Reproduce

1. After new install or upgrade of 1.13.x, notice new Gemini widget on the new tab page for new and existing users.
2. Users should be able to add/hide widget and connect an account to Gemini

Design:

Note to QA to refer to additional screens in Figma.

Brave version (brave://version info)

Targeting Brave 1.13.x

Version/Channel Information:

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

Other Additional Information:

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

Miscellaneous Information:

Fixed with brave/brave-core#6062

Related fixes:

• [Desktop] Gemini widget with translated text overlap making it hard to read [Desktop] Gemini widget with translated text overlap making it hard to read #10742 - [Desktop] user funds do not move to Uphold - follow up to 8428 #11298
• [Desktop] Show estimated conversion value in confirm trade window [Desktop] Show estimated conversion value in confirm trade window #10756 - [Desktop] Show estimated conversion value in confirm trade window #10756
• [Desktop] Transaction countdown timer speeds up after reconnecting to the network [Desktop] Transaction countdown timer speeds up after reconnecting to the network #10763 - [Desktop] Transaction countdown timer speeds up after reconnecting to the network #10763
• Remove the "No Thank You" opt-out from the Gemini widget Remove the "No Thank You" opt-out from the Gemini widget #10823 - Remove the "No Thank You" opt-out from the Gemini widget #10823
• Refresh token should be used in re-authorization flow (Gemini) Refresh token should be used in re-authorization flow (Gemini) #10978 - Refresh token should be used in re-authorization flow (Gemini) #10978
• Gemini widget should use updated trading scopes Gemini widget should use updated trading scopes #11030 - Gemini widget should use updated trading scopes #11030
• Update Gemini widget Oauth flow to use PKCE Update Gemini widget Oauth flow to use PKCE #11043 - Update Gemini widget Oauth flow to use PKCE #11043
• Sell panel should include to the total amount to be received in USD (Gemini) Sell panel should include to the total amount to be received in USD (Gemini) #11046 - Sell panel should include to the total amount to be received in USD (Gemini) #11046