Optimize ConcatByteSlices to avoid repeated reallocations

[soniseth0]

precompute the total concatenated length in ConcatByteSlices, allocate the output slice once with the exact capacity, keep existing behavior for empty or nil inputs while removing redundant allocations

[joshuacolvin0]

LGTM

[Copilot]

Pull request overview

This PR optimizes the ConcatByteSlices function to improve performance by eliminating repeated slice reallocations. Instead of starting with an empty slice and allowing append operations to trigger multiple reallocations as capacity is exceeded, the function now pre-calculates the total required capacity and allocates the output slice once with the exact size needed.

Key changes:

• Pre-computes total length of all input slices before concatenation
• Allocates output slice with exact capacity upfront using make([]byte, 0, totalLen)

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