perf(Bundler): reduce gas usage w/ unchecked increments in batch fn loops and cached user value

[horsefacts]

Motivation

Remove checks for lists to save gas usage because we know the index can't be incremented greater than an array's length.

Change Summary

• Add unchecked blocks to incrementing loop index in batch functions (register and trustedBatchRegister)
• Cache users[i] w/ UserData calldata user = users[i]

Merge Checklist

Choose all relevant options below by adding an x now or at any time before submitting for review

• [x] The PR title adheres to the conventional commits standard
• [x] The PR has been tagged with change type label(s) (i.e. documentation, feature, bugfix, or chore)
• [x] The PR's changes adhere to all the requirements in the contribution guidelines
• [x] This PR does not require changes to the Farcaster protocol

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PR-Codex overview

Focus of the PR:

This PR focuses on optimizing gas usage in the BundleRegistryGasUsageTest and Bundler contracts.

Detailed summary:

• Gas usage in the BundleRegistryGasUsageTest:testGasTrustedBatchRegister() function is reduced from 6,742,022 to 6,644,222.
• Gas usage in the IdRegistryGasUsageTest:testGasRegister() function is reduced from 734,576 to 664,422.
• Gas usage in the IdRegistryGasUsageTest:testGasRegisterForAndRecover() function is reduced from 1,704,136 to 1,704,136.
• In the Bundler.sol contract, a loop condition is changed from i < signers.length to i < signers.length;, and an unchecked block is added to increment i inside the loop.
• In the Bundler.sol contract, a loop condition is changed from i < users.length to i < users.length;, and an unchecked block is added to increment i inside the loop.

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[github-actions[bot]]

Coverage after merging fiveoutofnine/perf-1 into main will be

98.71%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src
Bundler.sol	100%	100%	100%	100%
FnameResolver.sol	100%	100%	100%	100%
IdRegistry.sol	100%	100%	100%	100%
KeyRegistry.sol	100%	100%	100%	100%
StorageRegistry.sol	100%	100%	100%	100%
src/lib
Signatures.sol	100%	100%	100%	100%
TransferHelper.sol	0%	0%	0%	0%	15, 15, 15, 25–26, 26, 26
TrustedCaller.sol	100%	100%	100%	100%