[rocsparse] Refactor conversion routine tests so that they conform to new test timing

[jsandham]

Motivation

This PR changes the conversion routine tests so that they conform to the test timing standards such that:

1. Quick tests complete in ~ O(1 s)
2. Pre_checkin tests complete in ~O(10 s)
3. Nightly tests complete in ~O(1 min)

Before:
[==========] 38222 tests from 76 test suites ran. (1113641 ms total)

After:
./rocsparse-test --gtest_filter=conversion-nightly
[==========] 25454 tests from 76 test suites ran. (408261 ms total)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #3952       +/-   ##
============================================
+ Coverage    47.83%   69.70%   +21.87%     
============================================
  Files          365      477      +112     
  Lines        51595    75651    +24056     
  Branches      5963    15541     +9578     
============================================
+ Hits         24678    52732    +28054     
+ Misses       24332    16437     -7895     
- Partials      2585     6482     +3897     

Flag	Coverage Δ
rocBLAS	?
rocSPARSE	69.70% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.
see 842 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.