feat: add Pausable to KeyRegistry

[horsefacts]

Motivation

Like our other contracts, the KeyRegistry should be pausable in case of emergency.

Change Summary

Add Pausable to KeyRegistry.

Merge Checklist

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• The PR title adheres to the conventional commits standard
• The PR has been tagged with change type label(s) (i.e. documentation, feature, bugfix, or chore)
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PR-Codex overview

Detailed summary

• The Pausable contract from OpenZeppelin is imported and added to the KeyRegistry contract.
• The pause() and unpause() functions are added to the KeyRegistry contract.
• The _registerFid() function is modified to check if the contract is paused before adding a key.
• The _remove() and _reset() functions are modified to check if the contract is paused before removing/resetting a key.
• Tests for adding, removing, and resetting keys are modified to check if the contract is paused before performing the respective operation.
• Tests for bulk adding and bulk resetting keys are modified to check if the contract is paused before performing the respective operation.
• A new test is added to check if only the admin can pause the contract.

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[github-actions]

Coverage after merging horsefacts/pausable-key-registry into main will be

98.98%

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%	12, 17, 20, 20, 20
TrustedCaller.sol	100%	100%	100%	100%
src/validators
SignedKeyRequestValidator.sol	100%	100%	100%	100%