Stop using `SysvarSerialize` with `solana-account`

[joncinque]

Problem

The SysvarSerialize trait is used in a lot of solana-account helpers to create sysvar accounts in the runtime, but most of these helpers boil down to using bincode::serialize_into with the sysvar id.

However, since the SysvarSerialize trait needs to be implemented on types like Rent and StakeHistory, we also need to keep those in sync when upgrading Agave. This caused a big annoyance during the most recent major version bumps in the SDK.

Proposed Solution

The SysvarSerialize trait isn't helping very much, and just creating more friction. To start, stop using the account helpers and just use bincode directly. After that, we can investigate removing the trait from the SDK totally, but that will be more destructive for on-chain devs.

[victorchukwuemeka]

Can I take up this task