Add 6 and 8 argument overloads to wiener_lpdf

[WardBrian]

From https://github.com/stan-dev/math/pull/2822 Scalar only for now, see #1373 for partial reason

I didn't add support for the optional precision_derivatives argument both of these have in C++. These would need to be data, which we don't currently support in the machinery for our distributions. We can add them manually or rethink this later.

Submission Checklist

• [x] Run unit tests
• Documentation
  • [ ] If a user-facing facing change was made, the documentation PR is here: TBD

Release notes

Exposed the new overloads of wiener_lpdf added to Stan Math by @Franzi2114

Copyright and Licensing

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the BSD 3-clause license (https://opensource.org/licenses/BSD-3-Clause)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 89.87%. Comparing base (8bc6ba0) to head (0ce17bf). Report is 3 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1411 +/- ## ======================================= Coverage 89.87% 89.87% ======================================= Files 63 63 Lines 10525 10529 +4 ======================================= + Hits 9459 9463 +4 Misses 1066 1066 ``` | [Files](https://app.codecov.io/gh/stan-dev/stanc3/pull/1411?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=stan-dev) | Coverage Δ | | |---|---|---| | [src/middle/Stan\_math\_signatures.ml](https://app.codecov.io/gh/stan-dev/stanc3/pull/1411?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=stan-dev#diff-c3JjL21pZGRsZS9TdGFuX21hdGhfc2lnbmF0dXJlcy5tbA==) | `98.02% <100.00%> (+<0.01%)` | :arrow_up: |