Migrate value rules to comparisons

Value rules in #[pina(validate(...))] are now comparisons over the field’s value or its len, so the annotation reads as the check it generates. The min, max, min_len, max_len, and exact_len parameter spellings are deprecated: they still parse and generate the identical checks, but each one warns at the parameter and names its replacement.

Nothing on the wire changes. Value rules are not recorded in the ABI document or migration manifests, and the deprecated spellings generate the same checks their replacements generate, so migrating an annotation is a rename, not a release.

Rewrite each named bound as a comparison

#![allow(unused)]
fn main() {
// before
#[pina(validate(min = 1, max = 1_000_000, error = TransferError::InvalidAmount))]
pub amount: u64,

// after
#[pina(validate(value >= 1 && value <= 1_000_000, error = TransferError::InvalidAmount))]
pub amount: u64,
}

Chain bounds on one receiver with && and separate rules with ,. A chain may also put the receiver in the middle, mirroring the range it checks:

#![allow(unused)]
fn main() {
#[pina(validate(100 < value <= u64::MAX))]
pub amount: u64,

#[pina(validate(4 < len <= 100))]
pub memo: String<100>,
}

Comparisons also express what the named bounds could not. Use value != 0 for a declarative non-zero check, or len != EXPR to reject one specific length.

What keeps its single =

Named parameters that are not comparisons keep their spelling:

• error = ERROR names the failure to raise, not a comparison. It stays in the validation group it overrides.
• validate(with = function) in the outer macro is a hook parameter and keeps =.
• Account rules in #[derive(Accounts)] — signer, address = EXPR, owner = EXPR, owners = EXPR, program = EXPR, sysvar = EXPR, data_len = EXPR, distinct_from = FIELD, empty, not_empty, writable, executable — are unchanged. Only value rules over value and len moved to comparisons.

Read the deprecation warning

Each deprecated parameter warns at the token the author wrote, which is the ordinary deprecated lint: #[allow(deprecated)] silences it and -D warnings fails on it.

warning: use of deprecated constant `_::PINA_DEPRECATED_VALIDATION_BOUND`: `min` is deprecated;
write the bound as a comparison, as in `value >= 1`
 --> src/lib.rs:8:22
  |
8 |     #[pina(validate(min = 1, max = 10))]
  |                      ^^^

The warning lowers to an empty const block, so it costs no compute units and adds no bytes to the program.

Type gates and duplicates carry over

A comparison is subject to the same gates its named bound was: value rules require an integer field (u8 through u128, i8 through i128, or the Pina Pod* integer types), and len rules require String<N>, PodString<N, PFX>, Vec<T, N>, PodVec<T, N, PFX>, or [u8; N]. Duplicates and the exact_len conflict are diagnosed the same way, spelled for the new grammar where the rule that triggered them is new.

See Declarative Validation for the complete rule table.