Incorrect buffer length handling for RGBA color data in readPntsColors function

[XinJack]

Describe the bug

The current implementation of the readPntsColors function contains a buffer length error when processing RGBA color data. The Uint8Array initialization for RGBA incorrectly uses nComponents (calculated as 3 * nPts) instead of 4 * nPts, leading to incomplete data reads and potential memory boundary violations.

itwinjs-core/core/frontend/src/internal/tile/PntsReader.ts

Line 94 in 49cd19f

const rgba = new Uint8Array(stream.arrayBuffer, dataOffset + pnts.RGBA.byteOffset, nComponents);

Also, the loop logic is wrong. It should iterates over 4 * nPts rather than nComponents (3 * nPts) with a step of 4. Besides, rgb index should be (i / 4) * 3, (i / 4) * 3 + 1, (i / 4) * 3 + 2 rather than i + 0, i + 1, i + 2.

itwinjs-core/core/frontend/src/internal/tile/PntsReader.ts

Line 95 in 49cd19f

for (let i = 0; i < nComponents; i += 4) {