Add a teacher count to the data export page

[Ghislain Hachey]

Add a new teacher count workbook available in the Data Export page of the EMIS.

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[Ghislain Hachey]

I’ve done an initial draft implementation of this. Unlike enrolments the TeacherActivity{Grouper} does not have much options for pivot table Column and Row fields (i.e. only Activity). But it’s a start and provides some insight into what could be next steps.

[Ghislain Hachey]

feat(Teachers): support for TeacherActivity Excel workbook export

Resolves #1358

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