Used pixelData to update texture instead of voxelManager to improve memory footprint

[ManojAgiliad]

Context

This changes is done to run the volumeViewport3D example and other example might not work with it.
We have introduced voxelManager to handle the data in cornerstone2.0, but while root causing the increased memory footprint I came across the logic that if we use pixelData directly instead of scalarData from voxelManager the memory consumption is low.

Changes & Results

Instead if creating voxelManager instance I have set it to null.
Used image pixelData instead of scalarData from voxelManager to update the texture.

Testing

I'm using the iPhone13 device for testing and instruments tool present on Mac to log the memory footprint

Checklist

PR

• [] My Pull Request title is descriptive, accurate and follows the
  semantic-release format and guidelines.

Code

• [] My code has been well-documented (function documentation, inline comments,
  etc.)

• [] I have run the yarn build:update-api to update the API documentation, and have
  committed the changes to this PR. (Read more here https://www.cornerstonejs.org/docs/contribute/update-api)

Public Documentation Updates

• [] The documentation page has been updated as necessary for any public API
  additions or removals.

Tested Environment

• [] "OS:
• [] "Node version:
• [] "Browser:

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