Prop 427: Signalling Proposal for Initial IBC Rate Limits

This proposal signals the implementation of initial rate-limiting criteria for net movements as specified below. These will be implemented in a future software upgrade.

## IBC Rate Limiting Background
The IBC Rate Limit module is a safety control implemented in v13, intended to protect assets on Osmosis in the event of security issues with:
* Osmosis
* A counter-party chain
* IBC

Rate limits allow only a specified net percentage change in the quantity of an asset on Osmosis within a specified time period.

This slows down the rate of any security incidents, allowing validators more time to respond, investigate and take any action required. Either capping the rate at which exploited tokens generated elsewhere can be sent to Osmosis for disposal or preventing unusually high amounts of tokens on Osmosis being removed.

## Proposed Values
As starting values this proposal will set the following for the largest assets, accounting for approximately 90% of all TVL on chain:

All Assets to be set to 30% in, 30% out within 24 hours and 60% in, 60% out within 7 days.

ATOM - ibc/27394FB092D2ECCD56123C74F36E4C1F926001CEADA9CA97EA622B25F41E5EB2
USDC - ibc/D189335C6E4A68B513C10AB227BF1C1D38C746766278BA3EEB4FB14124F1D858
WBTC - ibc/D1542AA8762DB13087D8364F3EA6509FD6F009A34F00426AF9E4F9FA85CBBF1F
WETH - ibc/EA1D43981D5C9A1C4AAEA9C23BB1D4FA126BA9BC7020A25E0AE4AA841EA25DC5
EVMOS - ibc/6AE98883D4D5D5FF9E50D7130F1305DA2FFA0C652D1DD9C123657C6B4EB2DF8A
STARS - ibc/987C17B11ABC2B20019178ACE62929FE9840202CE79498E29FE8E5CB02B7C0A4
DAI - ibc/0CD3A0285E1341859B5E86B6AB7682F023D03E97607CCC1DC95706411D866DF7
JUNO - ibc/46B44899322F3CD854D2D46DEEF881958467CDD4B3B10086DA49296BBED94BED
CRO - ibc/E6931F78057F7CC5DA0FD6CEF82FF39373A6E0452BF1FD76910B93292CF356C1

Proposed Values Table

## Justification
Liquid staking assets are not included in this proposal as spikes in movement would occur in the event of a depeg event to stabilise the peg.

The 24 hour period was chosen in order to give validators across time zones a chance to act on any questionable behavious detected while resetting frequently enough that extreme market conditions are able to be reflected on Osmosis.

The 7 day backup period was chosen in case the 24 hour period was not sufficient for validator action to occur.

Limits set should be well outside peak usage and so not affect users using the exchange normally.

Token variance day by day since launch shows that the greatest variance by far happened during May 2022.
Token Variance

Confining this chart to the May and June 2022 period, which covers the UST depeg event as well as the v9 chain halt, shows that most variance was caused by newly listed and incentivised Axelar and Evmos tokens gathering liquidity.
Terra Depeg and Chain Halt Token Variance

Examining the Negative axis only - the impact of the USDT depeg and the funds temporarily lost during the v9 exploit can be seen. The proposed rate limits would have been triggered on alternative stablecoins during the Terra depeg event and prevented the v9 exploit from getting worse in the event that it had not been caught as quickly as it was.
Terra Depeg and Chain Halt Token Variance, Negative Only

Excluding freshly launched tokens from the picture also gives a view that net change reduces the longer a token has been listed. This may correlate to deeper liquidity but shows that these rate limits should be only implemented on high liquidity, established tokens, as well as being regularly reviewed. Token Variance excluding first month of listing

Commonwealth Thread: https://commonwealth.im/osmosis/discussion/8543-set-ibc-rate-limits