First iteration of plans store

[alshakero]

Changes proposed in this Pull Request

This PR is the first iteration for the store of our plans in Gutenboarding.

Note: I put the files under stores dir as opposed to gutenboarding/lib/plans.ts for consistency. Files under gutenboarding/lib/plans.ts can be removed after this.

Related to #41787.

[matticbot]

Test live: https://calypso.live/?branch=add/plan-store

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

App Entrypoints (~1 bytes removed 📉 [gzipped])

name                 parsed_size           gzip_size
entry-gutenboarding        -25 B  (-0.0%)       -1 B  (-0.0%)

Common code that is always downloaded and parsed every time the app is loaded, no matter which route is used.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[razvanpapadopol]

This seems like a good start to have proper selectors and state handling for the plan selection feature. We just need to preserve the existing functionality so the domain could be set, in the order of importance, from:

• selecting from PlansGrid
• having the plan slug in the URL
• selecting a paid domain

[razvanpapadopol]

By removing this, we are breaking 2 existing functionalities (detailed in #41471 and #41679):

• getting plan from URL.
• replacing Free plan (shown by default) with a paid default version (eg: Personal) when the user picks a paid domain.

I suggest:

1. creating a selector for defaultPlan
2. calling useEffect with planPath and hasPaidDomain as dependencies to dispatch setPlan only when there is no selected plan.

[razvanpapadopol]

We should leave it undefined unless there is explicitly set by using /beginner route or using the PlansGrid.

[razvanpapadopol]

🚀