Update Play Billing Library

[deeppandya]

Description

We need to upgrade billing client dependency to 7.0.0.

[kjozwiak]

Used the same STR/Cases that were completed via #40078 (comment) after discussing with @deeppandya.

Verification PASSED on Pixel 6 Pro running Android 15 using the following build(s):

Brave | 1.69.147 Chromium: 128.0.6613.40 (Official Build) (64-bit)
--- | ---
Revision | d29b1747d0f906239936b0d94c40889920ebf2c0
OS | Android 15; Build/AP31.240617.015; 35; REL

Test Case #1 - New GPS Account (has never subscribed to premium)

• created a brand new Google account and @deeppandya added it into the GPS internal release channel
• verified that the new account had access to 1.69.147 Chromium: 128.0.6613.40 via the internal release test channel
• downloaded/launched 1.69.147 Chromium: 128.0.6613.40
• tapped on the Hamburger Menu -> VPN -> 7 Day Free Trial
• ensured that the purchase card was being displayed without any issues
• ensured that you can run through the Billing API and subscribe/enable VPN

Example	Example	Example	Example	Example	Example	Example	Example

Test Case #2 - Using previous/older account (has subscribed to Premium before)

• download/installed 1.68.137 Chromium: 127.0.6533.100
• upgraded from 1.68.137 Chromium: 127.0.6533.100 --> 1.69.147 Chromium: 128.0.6613.40 via the internal test channel
• tapped on the Hamburger Menu -> VPN -> 7 Day Free Trial
• ensured that the purchase card was being displayed without any issues (used the test card for this case as discussed)

Example	Example	Example	Example

[Uni-verse]

Verified on Samsung Galaxy S21 running Android 13 using version:

Brave	1.69.147 Chromium: 128.0.6613.40 (Official Build) (64-bit) 
Revision	d29b1747d0f906239936b0d94c40889920ebf2c0
OS	Android 13; Build/TP1A.220624.014; 33; REL

Test Case: New GPS Account (never subscribed)

• created a brand new Google account and added it into the GPS internal release channel
• verified that the new account had access to 1.69.147 Chromium: 128.0.6613.40 via the internal release test channel
• downloaded/launched 1.69.147 Chromium: 128.0.6613.40
• tapped on the Hamburger Menu -> VPN -> 7 Day Free Trial
• ensured that the purchase card was being displayed without any issues
• ensured that you can run through the Billing API and subscribe/enable VPN

Example	Example	Example	Example	Example	Example	Example

Test Case: Existing GPS Account (subscribed before)

• download/installed 1.68.137 Chromium: 127.0.6533.100
• upgraded from 1.68.137 Chromium: 127.0.6533.100 --> 1.69.147 Chromium: 128.0.6613.40 via the internal test channel
• tapped on the Hamburger Menu -> VPN -> 7 Day Free Trial
• ensured that the purchase card was being displayed without any issues (used the test card for this case as discussed)

Example	Example	Example