Update image volume options to replace bind with anonymous

[MayorFaj]

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Does this PR introduce a user-facing change?

None

Fixes: #27674

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[MayorFaj]

This PR corrects documentation strings in the code to use the accurate terminology "anonymous" instead of the misleading "bind" for the --image-volume option. The actual runtime behavior is unchanged - only help text and autocomplete suggestions are updated to reflect what the code already does.

The changes are:

• cmd/podman/common/completion.go - Autocomplete suggestion strings
• cmd/podman/common/create.go - CLI help text
• docs/ - Documentation files

The existing test at test/system/160-volumes.bats:540 already uses --image-volume anonymous correctly, so no test updates are needed.

Could a maintainer please add the No New Tests label? This is a documentation/help text correction that doesn't change runtime behavior or introduce new functionality that could regress.