Purchases: Revamp Cancellation Flow, take 1 (originally 93211)

[sirbrillig]

Proposed Changes

This PR refactors the purchase cancellation flow.

All the work was done originally by @Aurorum in #93211. This PR is just to move the branch to the calypso repo so that its strings can be translated (see #93211 (comment)).

However, because the other PR contained a merge commit, somehow that seems to have hidden large conflicts with #94213. I've tried my best to resolve them here but I'm not certain about some things.

Unresolved questions from the conflict:

• Does the purchase object actually have a siteUrl property? If so we need to modify the type. (See this comment.)
• In Purchases: Update cancellation page's support link to use Odie #94213 the code uses a boolean showSupportLink to determine which types of dialogs should not show the support link (it looks like domain stuff) but in Purchases: Revamp Cancellation Flow #93211 showSupportLink was removed. Should we remove the support link entirely or show it all the time?

I've started converting some of the files to TypeScript to help gain some confidence in the conflict resolution.

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[sirbrillig]

@jjchrisdiehl I could use your help with some of the questions I ran into with the merge conflict.

• Does the purchase object actually have a siteUrl property? If so we need to modify the type. (See this comment.)
• In Purchases: Update cancellation page's support link to use Odie #94213 the code uses a boolean showSupportLink to determine which types of dialogs should not show the support link (it looks like domain stuff) but in Purchases: Revamp Cancellation Flow #93211 showSupportLink was removed. Should we remove the support link entirely or show it all the time?

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• blaze-dashboard
• command-palette-wp-admin
• happy-blocks
• help-center
• notifications
• odyssey-stats
• whats-new

To test WordPress.com changes, run install-plugin.sh $pluginSlug update/cancel-purchase-page-93211 on your sandbox.

[sirbrillig]

From Slack discussions, @jjchrisdiehl and I have determined that:

• siteUrl does not exist on the purchase object, so we should remove it entirely.
• showSupportLink should remain and be false when the purchase is for a Jetpack (or I think any non-wpcom) product.

[sirbrillig]

There may have been some errors getting the original branch right. I'm trying again in #95065