(5P) FSE: Explore performance improvement options for BlockPreview

[obenland]

This should be a rather timeboxed task to determine how we can cut down the template selector load time to under 1 second. If we find that it's not possible for us to do so, let's go forward with #35232.

Let's consider researching the following items:

• Only loading visible contents (maybe the first X Blocks)
• Dynamically loading full template Blocks only on :hover (interaction)
• Ability to define X number of Blocks to load
• Memoization (59beaa8)
• Small images for thumbnails preview
• Compare performance loading static images
• Try adding a new thumbnail field in the endpoint response
• Move parsing templates content to higher component: https://github.com/Automattic/wp-calypso/pull

[getdave]

Do we have input from @youknowriad on possible avenues to explore here in terms of performance?

[getdave]

Some avenues:

• Only loading visible contents (maybe the first X Blocks)
• Dynamically loading full template Blocks only on :hover (interaction)
• Ability to define X number of Blocks to load
• Memoization

[retrofox]

I've defined the number of blocks to load until 10.

[obenland]

Optimized images and updated json annotation for EN: D31446-code