Name job pieces consistently when calling numberOfWorkUnits()

[jhlegarreta]

Description

Since the new multi-threading mechanism has been put in place, the notion of job pieces has transitioned from number of threads to number of work units (commit ce15429 and the related work). At many points in the code, the variable holding this number has not been renamed: e.g.

ThreadIdType numberOfThreads = this->GetNumberOfWorkUnits();

such as in

ITK/Modules/Filtering/ImageIntensity/include/itkShiftScaleImageFilter.hxx

Line 52 in 22ef020

ThreadIdType numberOfThreads = this->GetNumberOfWorkUnits();

In fact no consistent naming is used for the variable holding such information (e.g. the name nbthreads can also be found).

This naming issue also applies to the remote modules.

Steps to Reproduce

Style change: no impact on the code.

Expected behavior

Increase consistency throughout the code.

Actual behavior

No impact in compilation/tests.

Reproducibility

Does not apply.

Versions

Current head in master branch.

Environment

Does not apply.

Additional Information

The issue was first discussed in PR 10 of the LabelErodeDilate remote module. Some proposals were also discussed.