fix: reduce the amount of useless allocations for errors on hot paths

[Ddystopia]

Hi, I noticed a bunch of strange allocations on my hot path and it turned out to be some .ok_or(SpiError::CursorNotFound(name.to_string()))? at pgrx/src/spi/client.rs:159, which was immediately dropped. I became upset and told claude to find all similar places there and make them like they should be, in ok_or_else and similar. I reviewed the code and I believe it is fine - and the changes are trivial.

[0xPoe]

Maybe we should consider enabling the or_fun_call lint if we accept these changes?

[Ddystopia]

It depends on what exactly you want. There were many cases of ok_or(something_static), or similar. If it will get flagged, I am concerned about developer experience, as the code will become uglier.