[24506] Add changes for custom buffer serialization

[MiguelCompany]

Description

• Added a new property that returns true for unbounded octet / uint8 sequences. It can be used from the templates as typecode.isBufferType.
• Pass the sequence's type code to the template that generates the cpp typename, so the new flag can be consulted.

Contributor Checklist

• Commit messages follow the project guidelines.
• 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.
• NO: Changes are backport compatible: they do NOT break ABI nor change library core behavior.
• Changes are API compatible.
• N/A: 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.