Feat: Proxy aware chain extensions

[LandynDev]

Description

Adds 12 proxy-delegated chain extension variants that allow a smart contract with proxy rights to manage on behalf of a proxied coldkey. Each handler accepts an on_behalf_of: AccountId parameter, verifies the ProxyType and dispatches the operation as the proxied account. ProxyType::Any is accepted as a superset of all types.

Related Issue

Closes #2566

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Breaking Change

This PR does not create a breaking change.
This introduces new proxy chain extensions to wrap runtime calls with correct proxy perms.

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run ./scripts/fix_rust.sh to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots

Unit Tests:

Additional Notes

[open-junius]

Should we check other ProxyType like Any also enable the add_stake call.

[open-junius]

All V2 extensions are not the upgrade or replace of V1. Could use the name like proxy_xxx.
Do you consider use the unique extension to implement them all. like proxy_execute(real_coldkey: AccountId, call: RuntimeCall). like in EVM precompile https://github.com/opentensor/subtensor/blob/main/precompiles/src/proxy.rs#L146.

[LandynDev]

All V2 extensions are not the upgrade or replace of V1. Could use the name like proxy_xxx. Do you consider use the unique extension to implement them all. like proxy_execute(real_coldkey: AccountId, call: RuntimeCall). like in EVM precompile https://github.com/opentensor/subtensor/blob/main/precompiles/src/proxy.rs#L146.

I went ahead and implemented this with Proxy* variants (e.g. ProxyAddStakeV1, ProxyRemoveStakeV1, etc.).

Regarding a single proxy_execute(real_coldkey, call: RuntimeCall) — I actually started with that approach (a generic proxy_call dispatcher that took SCALE-encoded RuntimeCall bytes). The problem is that ink! contract developers would have to manually SCALE-encode the target function selector and all arguments into raw bytes. Found it to be error-prone and a poor developer experience.

I pretty much just implemented it how the Caller* variants were done in #2550.