mbedtls: update to 3.6.4 in 4.1 branch

[ceolin]

Describe the bug

3.6.4 release contains fixes for the following vulnerabilities

• CVE-2025-49601
• CVE-2025-49600
• CVE-2025-52496
• CVE-2025-47917
• CVE-2025-48965
• CVE-2025-52497
• CVE-2025-49087

And several other bug fixes that must back ported to 4.1 branch.

[github-actions]

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