[Merged by Bors] - Support multiple previous ATXs

[poszu]

Motivation

Add support for multiple previous ATXs as a merged ATX might reference multiple ATXs.

Description

• extended the existing migration 21 to take the previous ATX from ATX blobs (assuming all ATXs are still V1) to speed up migrations
• added prev_atxid column in posts table to show which ATXID was used by a given nodeID in a given ATX (it will be needed for invalid prev atx malfeasance proofs).

Test Plan

TODO

• Explain motivation or link existing issue(s)
• Test changes and document test plan
• Update documentation as needed
• Update changelog as needed

[codecov]

Codecov Report

Attention: Patch coverage is 84.27673% with 25 lines in your changes missing coverage. Please review.

Project coverage is 82.0%. Comparing base (fcce5d8) to head (549dd0f).

Files	Patch %	Lines
api/grpcserver/activation_service.go	62.5%	5 Missing and 1 partial ⚠️
api/grpcserver/mesh_service.go	50.0%	5 Missing and 1 partial ⚠️
sql/atxs/atxs.go	91.3%	2 Missing and 2 partials ⚠️
sql/migrations/state_0021_migration.go	63.6%	1 Missing and 3 partials ⚠️
activation/validation.go	93.9%	1 Missing and 1 partial ⚠️
datastore/store.go	0.0%	2 Missing ⚠️
activation/handler_v2.go	97.3%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #6024     +/-   ##
=========================================
- Coverage     82.1%   82.0%   -0.1%     
=========================================
  Files          308     308             
  Lines        34067   34123     +56     
=========================================
+ Hits         27971   28009     +38     
- Misses        4325    4338     +13     
- Partials      1771    1776      +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[poszu]

Bors merge

[spacemesh-bors]

Pull request successfully merged into develop.

Build succeeded:

• systest-status
• ci-status