Add option to have multiple unit test reports in the pkgdown documentation

[walkowif]

Closes https://github.com/insightsengineering/idr-tasks/issues/793.

Example workflows:

• teal
• tern

In order to use this functionality in a repository, this kind of workflow update is required:
walkowif/teal@main...walkowif:teal:non-cran-unit-test-report
walkowif/tern@main...walkowif:tern:non-cran-unit-test-report

[github-actions]

Code Coverage Summary

Filename      Stmts    Miss  Cover    Missing
----------  -------  ------  -------  ---------
R/hello.R        20       6  70.00%   55-60
TOTAL            20       6  70.00%

Diff against main

Filename      Stmts    Miss  Cover
----------  -------  ------  --------
TOTAL             0       0  +100.00%

Results for commit: cd5aaf6

Minimum allowed coverage is 80%

♻️ This comment has been updated with latest results

[github-actions]

Unit Tests Summary

3 tests   3 ✅  6s ⏱️
3 suites  0 💤
1 files    0 ❌

Results for commit cd5aaf6.

♻️ This comment has been updated with latest results.

[github-actions]

Unit Test Performance Difference

Test Suite	$Status$	Time on main	$±Time$	$±Tests$	$±Skipped$	$±Failures$	$±Errors$
shiny	💔	$2.42$	$+7.86$	$0$	$+1$	$0$	$0$

Additional test case details

Test Suite	$Status$	Time on main	$±Time$	Test Case
shiny	💔	$2.42$	$+7.86$	The_Shiny_App_returns_a_proper_greeting

Results for commit 34e5b59

♻️ This comment has been updated with latest results.