Fix item price in purchase event

[jorgemd24]

Changes proposed in this Pull Request:

Closes #2181 .

The purchase event on the Order confirmation page was displaying the wrong price for each item. Instead of showing the individual item's price, it was reflecting the total amount for that line.

For example, if we have an item priced at 3€ and we purchase 2 units:

Before:

After:

Detailed test instructions:

1. Open an incognito window.
2. Purchase a product and add more than 1 unit to the cart.
3. Finish the order.
4. Use the Google Analytics debugger extension, GA4 Debug View, or inspect the code on the Order confirmation page.
5. Check that the purchase event -> items -> price aligns with the product price.

Additional details:

@mikkamp suggested that a nice way to test these scenarios by including wp_print_inline_script_tag into the WP Proxy class, enabling us to test various outcomes. I'll create a follow-up issue to focus on this.

Changelog entry

Fix - item price in purchase event.

[codecov]

Codecov Report

Merging #2184 (d65b577) into develop (2b9b5ae) will not change coverage.
Report is 51 commits behind head on develop.
The diff coverage is 62.5%.

Additional details and impacted files

@@            Coverage Diff            @@
##             develop   #2184   +/-   ##
=========================================
  Coverage       58.2%   58.2%           
  Complexity      4127    4127           
=========================================
  Files            453     453           
  Lines          17691   17691           
=========================================
  Hits           10300   10300           
  Misses          7391    7391           

Flag	Coverage Δ
php-unit-tests	58.2% <62.5%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/DB/Table.php	9.1% <ø> (ø)
src/DB/TableInterface.php	0.0% <ø> (ø)
src/Infrastructure/GoogleListingsAndAdsPlugin.php	0.0% <ø> (ø)
src/Shipping/ZoneMethodsParser.php	98.4% <100.0%> (ø)
google-listings-and-ads.php	6.2% <0.0%> (ø)
src/DB/Migration/Migration20231109T1653383133.php	0.0% <0.0%> (ø)
src/Google/GlobalSiteTag.php	0.0% <0.0%> (ø)

[puntope]

Thx @jorgemd24 LGTM

I tested adding 4 units and it showed only the price per unit.

Also, I tested with decimals as I saw there was a round param in that new function.