perf: optimize ReentrancyGuardTransient with pre-computed BooleanSlot

[borj404]

Description

Eliminates redundant type casting in ReentrancyGuardTransient by pre-computing the BooleanSlot wrapper at compile-time.

Edit: Updated to support the new nonReentrantView modifier introduced in the latest version.

Current implementation

Current implementation performs asBoolean() → BooleanSlot.wrap() three times per nonReentrant execution (10 gas each).

Optimization

Pre-computed constant:

TransientSlot.BooleanSlot private constant REENTRANCY_SLOT =
    TransientSlot.BooleanSlot.wrap(REENTRANCY_GUARD_STORAGE);

Gas Savings

19 gas per nonReentrant call (verified via test suite)

Method	Original gas	Optimized gas	Savings	Improvement
callback()	44,007	43,988	19 gas	0.04%
guardedCheckEntered()	21,952	21,933	19 gas	0.09%

Deployment overhead: 1,728 gas (amortized after ~91 transactions)

Testing

• All existing tests pass unmodified.
• Full benchmark: https://github.com/borj404/openzeppelin-transient-reentrancy-gas-optimization/tree/optimize/reentrancy-guard-transient

Impact

• Zero security trade-offs.
• Full backward compatibility.
• Supports both nonReentrant and nonReentrantView modifiers.

[changeset-bot]

🦋 Changeset detected

Latest commit: 7627ddb

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
openzeppelin-solidity	Patch

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