[24101] Fix build in GCC 15 (backport #6263)

[mergify]

Description

Fix compilation with GCC 15 by adding missing #include <cstdint> to SharedSecretHandle.h.
GCC 15 is stricter about implicit includes, and uint8_t requires an explicit #include <cstdint>. Without this include, compilation fails with errors like:

error: 'uint8_t' was not declared in this scope

Additionally, GCC 15 shows a false positive warning in sqlite3.c:

warning: ‘strlen’ reading 1 or more bytes from a region of size 0 [-Wstringop-overread]
35253 |   return 0x3fffffff & (int)strlen(z);

Which is fixed in this PR by changing the if statement to a ternary operator.

@Mergifyio backport 3.4.x 3.3.x 3.2.x 2.14.x

Fixes #6254

Contributor Checklist

• Commit messages follow the project guidelines.

• The code follows the style guidelines of this project.

• N/A Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally

• N/A Any new/modified methods have been properly documented using Doxygen.

• N/A Any new configuration API has an equivalent XML API (with the corresponding XSD extension)

• Changes are backport compatible: they do NOT break ABI nor change library core behavior.

• Changes are API compatible.

• N/A New feature has been added to the versions.md file (if applicable).

• N/A New feature has been documented/Current behavior is correctly described in the documentation.

• Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• N/A: If this is a critical bug fix, backports to the critical-only supported branches have been requested.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

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This is an automatic backport of pull request #6263 done by [Mergify](https://mergify.com).

[mergify]

🧪 CI Insights

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❌ Job Failures

Pipeline	Job	Health on 3.3.x	Retries	🔍 CI Insights	📄 Logs
Fast DDS MacOS CI	mac-ci / fastdds_test ()		0	View	View
Fast DDS Windows CI	windows-ci / fastdds_test (RelWithDebInfo, examples), v143		0	View	View
	windows-ci / fastdds_test (RelWithDebInfo, unittest-II), v142		0	View	View