MIP 6 (slot reduction to 90s) implementation

[cjjdespres]

This is the implementation of the changes proposed in the MIP https://github.com/MinaProtocol/MIPs/blob/main/MIPS/mip-0006-slot-reduction-90s.md. Specifically, it implements those changes that require a hard fork (slot time and coinbase reduction) or that we want to apply only after the hard fork (removing the soft zkapp limit). It sets the daemon's default slot time to 90s (90000 ms) instead of the current 180s, for both the mainnet and devnet build profiles. It also sets the coinbase to 360 instead of the current 720 on the mainnet, devnet, and lightnet build profiles. Finally, it sets the default zkapp_cmd_limit (the soft limit) to None in all build profiles by removing that config entry from the mainnet and devnet profiles (the only ones that have that limit).

Closes: #18048

[glyh]

sure, but let's wait until OCV, I'll merge them into mesa-testing for now.

[glyh]

There's 2 other changes in that MIP

• update vesting logic
• remove zkapp soft limit

Are they already implemented & merged somewhere else?