Lint 10: sysvar-address-check

[oslfmt]

Short and sweet lint that addresses this issue by flagging any calls to bincode::deserialize() (resolving to a type implementing Sysvar trait) and advising user to use from_account_info() instead (the way they should do it).

There could be another variation of this lint that performs a key check. This variation has the trade-off that it will avoid false positives, but if the key check is not robust enough, it will leave out some cases we want to catch.

There are many ways to perform a key check. Referencing the key field directly, calling key() (from anchor), unsigned_key(), to name a few. Then there could be != or == checks. With this in mind, I think it's difficult to implement a good key check, and better to just recommend using from_account_info().

[CLAassistant]

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