Migrate away from deprecated ioutil

[sebrandon1]

ioutil has been deprecated since Go 1.16: https://go.dev/doc/go1.16#ioutil

Tracking issue: redhat-best-practices-for-k8s/telco-bot#52

Migration from ioutil to os/io and related refactoring:

• Replaced ioutil.ReadFile, ioutil.WriteFile, and ioutil.ReadAll with os.ReadFile, os.WriteFile, and io.ReadAll respectively across all affected files. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]
• Updated all instances of ioutil.Discard to io.Discard for logger initialization and null logging. [1] [2] [3] [4]

Directory reading and file info handling:

• Refactored usages of ioutil.ReadDir to use os.ReadDir, and reconstructed []os.FileInfo slices by calling .Info() on each directory entry, ensuring compatibility with the new API. This impacts methods in pkg/fswrap/fswrap.go and pkg/machineinformer/relocatablesysfs.go. [1] [2] [3]

Test and temporary file management updates:

• Replaced ioutil.TempDir with os.MkdirTemp in test files for creating temporary directories, and updated test file writing to use os.WriteFile. [1] [2] [3] [4] [5] [6]

General import cleanup:

• Removed unused ioutil imports and updated import blocks to use os and io as needed. [1] [2] [3] [4] [5] [6] [7] [8]

These changes modernize the codebase and remove reliance on deprecated APIs, improving maintainability and future compatibility.

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[sebrandon1]

/retest