[General] Avoid unnecessary object allocations

[j-piasecki]

Description

Removes unnecessary object allocations:

• configUtils - instead of using Object.assign and creating an object with a single key, the value is now assigned directly
• eventHandlerUtils - instead of allocating an object for each callback (even when undefined), the value is now assigned directly
• reanimatedUtils - instead of iterating over the entire config, allocating a [key, value] tuple for each field, iterate over the known callbacks

Test plan

Run the example app

[Copilot]

Pull request overview

This PR reduces avoidable object/tuple allocations in the v3 hook utilities by replacing generic iteration/spread patterns with direct property assignment and fixed-key iteration, lowering per-render/per-gesture overhead in hot paths.

Changes:

• reanimatedUtils: switch from Object.entries(config) scanning to iterating known callback keys to detect worklet handlers.
• eventHandlersUtils: avoid creating intermediate objects via conditional spreads when memoizing gesture callbacks.
• configUtils: replace Object.assign + single-key object creation with direct assignment into the filtered config.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/react-native-gesture-handler/src/v3/hooks/utils/reanimatedUtils.ts	Avoids Object.entries tuple allocations by iterating the known callback key set when checking for worklet handlers.
packages/react-native-gesture-handler/src/v3/hooks/utils/eventHandlersUtils.ts	Avoids conditional-spread object allocations when building the memoized callbacks object.
packages/react-native-gesture-handler/src/v3/hooks/utils/configUtils.ts	Avoids allocating { [key]: value } objects by assigning filtered config props directly.

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