runtime-sdk: Implement message emission gas

[kostko]

Previously one had to explicitly configure the maximum number of messages to consensus layer that can be emitted by a transaction. This posed a problem for Ethereum-compatible transactions which don't support this field.

This implementation adds message emission gas which is dynamically calculated based on MAX_BATCH_GAS and MAX_MESSAGES. Similar to storage gas, it is only charged in case other use is too small in order to limit the total number of messages that can be emitted in a batch.

All Ethereum-compatible transactions now use this dynamic limit for the maximum number of consensus messages to be emitted.

[netlify]

✅ Deploy Preview for oasisprotocol-oasis-sdk canceled.

Name	Link
🔨 Latest commit	bbd26a9
🔍 Latest deploy log	https://app.netlify.com/sites/oasisprotocol-oasis-sdk/deploys/65f47f525a738f0008414323

[codecov]

Codecov Report

Attention: Patch coverage is 73.91304% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 65.28%. Comparing base (e7e0b93) to head (bbd26a9).

Files	Patch %	Lines
runtime-sdk/src/modules/core/mod.rs	73.33%	4 Missing ⚠️
runtime-sdk/src/modules/consensus/mod.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1662      +/-   ##
==========================================
+ Coverage   65.25%   65.28%   +0.03%     
==========================================
  Files         114      114              
  Lines        8349     8365      +16     
==========================================
+ Hits         5448     5461      +13     
- Misses       2901     2904       +3     

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

[CedarMist]

I've tested this locally with multiple delegations (10 as an example) and it works as expected.

Performing 10 delegations this costs 1171870 gas, so with a 15mm gas limit this allows 128 delegations.

I have a branch in sapphire-paratime which adds a test for this: oasisprotocol/sapphire-paratime#287

[CedarMist]

This works for me, I have not reviewed the code though.

[peternose]

Wouldn't it be better to use max u32 instead of 0 to indicate that up to the maximum number of per-batch messages can be emitted? Maybe we even need zero to disallow consensus messages.

[kostko]

I think using zero makes it easier to use because this field is already deployed and just omitting the field will result in the new behavior be in effect (which makes the most sense for most use cases). There is no reason to actually have this field now, and we can consider removing it in a later iteration.