Update PXE app-siloed tag indices from contract

[nventuro]

Once we can fetch app-siloed secrets and indices via #9365, we'll need a way to update these indices to avoid computing the same tags again in the future. This simply means passing whatever index value and storing it as the latest index for that (secret, app_address) pair.

Note that PXE needs to keep track both of the last seen recipient index as well as the last used sender index, and so methods should exist to update either of them.

In the future when this runs from aztec.nr we'll want to validate that the oracle call originated in the correct address, to avoid contracts interfering with each other secrets, but this should not be strictly required since contracts should not know about each other's app-siloed secrets.

[sklppy88]

Closed as completed by #9573