Wrong gas estimates for encrypted ParaTime transfers

[matevz]

Trying to transfer tokens from the secp256k1 account on Sapphire and providing --encrypted incorrectly estimates gas:

1. first attempt (no --gas-limit provided):

Broadcasting transaction...
Error: Transaction check failed with error: module: core code: 12 message: out of gas (limit: 2318 wanted: 11388)

2. second attempt --gas-limit 11388:

Broadcasting transaction...
Error: Transaction check failed with error: module: core code: 12 message: out of gas (limit: 11388 wanted: 11389)

3. third attempt --gas-limit 11389:

Broadcasting transaction...
Error: Transaction check failed with error: module: core code: 12 message: out of gas (limit: 11389 wanted: 11390)

4. fourth attempt --gas-limit 11390:

Broadcasting transaction...
Transaction included in block successfully.
Round:            3995161
Transaction hash: 1dc1246a30e854dede27d48cb1220b4c19d46521ade38622bbda3ea8c2a4e738
                  (Transaction result is encrypted.)
Error: Execution failed with error: module: core code: 12 message: core: out of gas (limit: 11390 wanted: 12389)

^^ the transaction was actually submitted and gas was spent, see: https://explorer.oasis.io/mainnet/sapphire/tx/1dc1246a30e854dede27d48cb1220b4c19d46521ade38622bbda3ea8c2a4e738

5. fifth attempt --gas-limit 12389 finally worked:

Broadcasting transaction...
Transaction included in block successfully.
Round:            3995186
Transaction hash: 7224d59e6b74d9b2caf55ab40dfe0757cef4f71c66d3a7aba3de1d267d2ea409
                  (Transaction result is encrypted.)
Execution successful.

Since gas estimates are standard for transactions such as ParaTime transfers and withdrawals, we could probably just hardcode those?

[kostko]

The problem is that currently the way CLI does gas estimation ignores encryption-related costs, because it assumes that the node it is talking to does not have access to the key manager committee so it estimates a plain transaction and uses that estimate.

To avoid changing this assumption, it could probably at least better guess the costs, for example by querying how much encryption-related stuff costs and adding that plus some extra per-byte costs due to encrypted transactions being slightly larger.