Coupons: Update product selector view buttons

[itsmeichigo]

Part of #6489

Description

This PR adds some adjustments to the buttons in the product selector view:

• Update the title of the view based on whether the view is for selecting or excluding products.
• Remove the Done button from the navigation bar and add one for completing the selection at the bottom.
• Add a banner on top of the product list with 2 buttons: Select All and Filter. The Select All button is not doing anything at the moment, and the Filter button only shows the filter screen and hasn't handled any filter updates yet.

In the next PR, we'll need to duplicate the current selector data source and add updates to that.

Testing instructions

Since the product selector screen hasn't got an entry point from the coupons flow, let's test the linked product flow instead.
With the couponEdit feature flag on:

• Navigate to the Products tab > select a Product > Add more details > Linked products > Add Products > Add Products.
• Notice that the title of the view now stays the same no matter how many products are selected.
• Notice that there's a bar at the top with 2 buttons: Select All and Filter.
• Select one or more products on the list. Notice that when there's at least one product selected, a button shows up at the bottom with a title indicating the number of products selected. Tapping this button completes the selection and dismisses the view.

With the couponEdit feature flag on: repeat the first step above and notice that the product selector view stay the same as before.

Screenshots

Before	After

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

You can test the changes on this Pull Request by downloading it from AppCenter here with build number: pr6603-ba47381. IPA is available here. If you need access to this, you can ask a maintainer to add you.

[pmusolino]

LGTM