net: posix: fix hostname config conflict with unique updates

[PragatiGarg-eaton]

Overview

Fixes Kconfig conflict between POSIX networking and unique hostname updates that was introduced in v3.7.1.

Problem

Enabling CONFIG_POSIX_API=y auto-selects CONFIG_POSIX_NETWORKING=y, which force-selects CONFIG_NET_HOSTNAME_DYNAMIC=y. This conflicts with CONFIG_NET_HOSTNAME_UNIQUE_UPDATE=y, preventing the use of POSIX networking with unique hostname updates.

Solution

Decouple NET_HOSTNAME_MAX_LEN from NET_HOSTNAME_DYNAMIC dependency:

• Remove forced selection of NET_HOSTNAME_DYNAMIC from POSIX networking
• Make hostname length configuration available independently
• Add build assertions - Ensure proper validation at compile time

Testing

• Verified fix resolves Kconfig conflicts
• Validated unique hostname update operations
• Confirmed hostname length constants are properly defined
• Build tests pass for various configuration combinations

Fixes #95811

[github-actions]

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[sonarqubecloud]

Quality Gate failed

Failed conditions
D Reliability Rating on New Code (required ≥ C)

See analysis details on SonarQube Cloud

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[cfriedt]

@PragatiGarg-eaton - tests need to pass in order for the change to be merged. Can you revisit?

Please feel free to jump on discord to ask for pointers for running failing tests.