gh-145866: Convert DICT_MERGE to leave its inputs on the stack to be cleaned up by _POP_TOP

[NekoAsakura]

• Issue: Convert more uops to leave their inputs on the stack to be cleaned up by _POP_TOP #145866

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[bedevere-app]

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[Fidget-Spinner]

Thanks for your contribution, and welcome to CPython :)!

[Fidget-Spinner]

@NekoAsakura sorry, for CPython we don't force push, as all commits are squash-merged. So just do normal commits and I'll squash it at the end. Thank you!

[NekoAsakura]

Thanks for your contribution, and welcome to CPython :)!

Thanks for the review and the warm welcome(^^)! Changes applied.

[Fidget-Spinner]

LGTM. Thanks!