fix: avoid leaking winston types

[Flarna]

Which problem is this PR solving?

Fixes #925

Short description of the changes

The winston instrumentation needs the winston types only internaly.
Move them into an internal file to avoid leaking it to end user.

Checklist

• Ran npm run test-all-versions for the edited package(s) on the latest commit if applicable.

[codecov]

Codecov Report

Merging #932 (48be567) into main (da792fe) will decrease coverage by 2.88%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #932      +/-   ##
==========================================
- Coverage   95.87%   92.98%   -2.89%     
==========================================
  Files          18       19       +1     
  Lines        1067     1155      +88     
  Branches      217      232      +15     
==========================================
+ Hits         1023     1074      +51     
- Misses         44       81      +37     

Impacted Files	Coverage Δ
...try-instrumentation-winston/src/instrumentation.ts	57.95% <ø> (ø)