Use maps.Clone() where appropriate

[montag451]

Go 1.21 introduced a new maps package which provides some utility functions to facilitate some common operations on map. One of these functions is maps.Clone which eases the cloning of a map. Moreover, the maps.Clone function is slightly more efficient than manual cloning (cf golang/go@b5a7f2e)

[montag451]

I missed the fact that maps.Clone return a nil map when the passed map is nil which lead to crashes in some parts of the code so I prefer to close the PR because the benefit of using maps.Clone is not as high as expected.