Max TPS Mixed mission is too pessimistic

[marta-lokhova]

it looks like currently our Max TPS Mixed Load mission is too aggressive

• Its instruction distribution is too pessimistic, which causes ledgers to take a long time to apply (~7 seconds)
• Its "Upload WASM" weight is too high, causing core to run into 5MB block size limitation for Soroban transactions.

We should configure the mission similarly to Classic Max TPS test, where the idea is to submit basic payment load in order to measure theoretical max TPS. For Soroban-related load tests, I think this means we can do only invoke host ops (so no wasm uploads), and tailor resource distributions to mimic payments.

[bboston7]

#220 fixes the first bullet point. I'll fix the second one once that merges.