Remove x/exp import

[julienrbrt]

I thought I created an issue after: #19598.
Turns out there is work towards it, so let's properly track it (ref: #19889)

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• Replaces x/exp/slices by std slices (refactor: use slices std #19598)
• Replace x/exp/maps by std maps (Note, some methods need to wait for Go 1.23 for the new functions of the maps packages)

Then let's not use x/exp ever again as they make no api guarantee for avoiding cases like this: #18415, #19593