Adds support for nested directories

[msutovsky-r7]

Fixes mkdir inconsistency. This address the inconsistency between mkdir among Meterpreter and other types of sessions.

[Copilot]

Pull request overview

Adds “mkdir -p” style behavior to Meterpreter’s mettle stdapi filesystem mkdir handler to align directory creation semantics with other session types.

Changes:

• Updates fs_mkdir to attempt creation of intermediate path components when given a nested directory path.
• Switches mkdir handling from a single eio_mkdir call to manual path splitting + per-component existence checks/creation.

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