Add buffer overflow detection

[bmribler]

This PR hardens H5C__decode_cache_image_header() by adding buffer overflow checks. It doesn't specifically address a CVE issue, but simply responds to this comment in PR #5841.

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Important

Add buffer overflow checks to H5C__decode_cache_image_header() in H5Cimage.c for security hardening.

• Security Hardening:
  • Add buffer overflow checks in H5C__decode_cache_image_header() in H5Cimage.c.
  • Use H5_IS_BUFFER_OVERFLOW() to verify buffer space before accessing elements.
  • Checks added for signature, version, flags, image data length, and number of entries.
• Misc:
  • Adjust H5C__reconstruct_cache_contents() to use updated buffer handling logic.

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[jhendersonHDF]

The buffer overflow check above if (H5_IS_BUFFER_OVERFLOW(p, H5C__MDCI_BLOCK_SIGNATURE_LEN, *buf + buf_size - 1)) should probably be updated to make use of p_end instead for consistency.

[bmribler]

@jhendersonHDF I made the change. Thanks!