chore: modernize codebase for go 1.25

[janos]

Checklist

• I have read the coding guide.
• My change requires a documentation update, and I have done it.
• I have added tests to cover my changes.
• I have filled out the description and linked the related issues.

Description

This PR updates the code only in formal way according to the language and standard library improvements over the years. It contains mainly the changes that go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix ./... command made and what linters suggested.

These changes should, and must, not change any existing behaviour.

Open API Spec Version Changes (if applicable)

Motivation and Context (Optional)

General code maintenance.

Related Issue (Optional)

Screenshots (if appropriate):

[gacevicljubisa]

This is great. It will prevent many of minor PRs, and it will reduce tme spent on checking on them. To bad that gopls is not provided by golangci-lint. Also it improves the code.