Merge pull request #29453 from vrabaud:persistence

Replace "static inline" by "inline" in headers #29453

This fixes #29436

I also replaced CV_INLINE which can be removed in a later PR.

I can make a similar PR for 4.x if you want.

### Pull Request Readiness Checklist

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- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/core/include/opencv2/core.hpp

@@ -3112,7 +3112,7 @@ public:
 
 };
 
-static inline
+inline
 String& operator << (String& out, Ptr<Formatted> fmtd)
 {
     fmtd->reset();
@@ -3121,7 +3121,7 @@ String& operator << (String& out, Ptr<Formatted> fmtd)
     return out;
 }
 
-static inline
+inline
 String& operator << (String& out, const Mat& mtx)
 {
     return out << Formatter::get()->format(mtx);