Draft: Adaptive inflation: add adaptive inflation vote toggle EMA in block metadata

Context

This MR follows !8661 (merged), which adds per block toggle vote for adaptive inflation. This MR adds the adaptive inflation vote toggle EMA value in block metadata.

Manually testing the MR

In !8661 (merged), when the value was in the block metadata, some tests would crash, like:

_build/default/tezt/tests/main.exe --verbose --file sc_rollup.ml --title 'Nairobi->Alpha: wasm_2_0_0 - node can read data after store migration'

This MR is still WIP, but it's expected to be small and easy enough to review.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR