SIMD-0194: Deprecate rent exemption threshold

[deanmlittle]

Implemented SDK changes outlined in SIMD-0194.

This allows us to remove f64 math from rent calculation saving a bunch of CUs in all newly deployed programs and making the rent_exemption_threshold value inert, simplifying any future changes to rent.

Before merging, I will need to:

• Get this PR approved SIMD-0194: Deprecate rent exemption threshold agave#7373
• Activate feature gate rent6iVy6PDoViPBeJ6k5EJQrkj62h7DPyLbWGHwjrC on all networks.
• Update the [deprecated(since = "2.3.X") message in two places once a release candidate has been decided upon.
• Submit a PR to Pinocchio to replicate the same functionality
• Make a follow up PR to update the JavaScript client.

Tagging @joncinque for review.

[github-actions]

If this PR represents a change to the sysvar layout, please open a follow-up PR to update the JavaScript client @solana/sysvars (example)
Thank you for keeping the JavaScript clients in sync with the Rust clients.

[febo]

@deanmlittle What do you think if we remove completely any reference to f64? We could do this in 2 steps. First a PR to add the deprecation messages followed by a patch release; a second PR with the refactoring to be used when the feature is activated, which eventually is published as a new major release.

[deanmlittle]

@deanmlittle What do you think if we remove completely any reference to f64? We could do this in 2 steps. First a PR to add the deprecation messages followed by a patch release; a second PR with the refactoring to be used when the feature is activated, which eventually is published as a new major release.

I would be very happy to replace it with a [u8;8] instead and place a clippy rule in to disallow floating point arithmetic, but I was originally trying to move as few things as possible. If there's appetite from your end, let's do it? I also think we can deprecate like half of the rent-related convenience functions in there too.

[febo]

@deanmlittle What do you think if we remove completely any reference to f64? We could do this in 2 steps. First a PR to add the deprecation messages followed by a patch release; a second PR with the refactoring to be used when the feature is activated, which eventually is published as a new major release.

I would be very happy to replace it with a [u8;8] instead and place a clippy rule in to disallow floating point arithmetic, but I was originally trying to move as few things as possible. If there's appetite from your end, let's do it? I also think we can deprecate like half of the rent-related convenience functions in there too.

I think we should and we can do it in two steps. The first one just deprecate stuff, so we don't actually change anything; then in the refactoring we remove all the stuff that won't be needed anymore after the feature activation.

Somewhat related to this, I had to remove all the f64 things so Alessandro could compile p-token with the upstream rustc ebpf target.

cc: @joncinque

[joncinque]

I think we should and we can do it in two steps. The first one just deprecate stuff, so we don't actually change anything; then in the refactoring we remove all the stuff that won't be needed anymore after the feature activation.

Yes, let's follow what Pinocchio did with anza-xyz/pinocchio#243 first, by deprecating the field and all rent-paying functions, so that we can rename the field and remove the concept of rent-paying in the next breaking change.