Improve data_src_qadc_csts_ext_test_app

What this MR does / why we need it:

It makes the data_src_qadc_csts_ext_test_app app a proper unit test (and also removes the test app and assembly) and adds some improvements to the test (I and Q data are different now). It also adds some new properties to the data_src_qadc_csts.hdl worker that allows it to send an eof after a certain number of samples.

Finally it does some other things such as fixing typos in the projects/assets/applications/data_src_qadc_test_app_csts/data_src_qadc_zcu104_fmcomms_2_3_test_app_csts.xml.

Steps to complete before submitting MR:

• I have read Contribution guidelines

Release Notes

N/A

Changelog

• enh(hdlbase): improve data_src_qadc_csts_ext_test_app and turn it into a proper unit test

Which issue(s) this MR closes

Closes #2371 (closed)