Add support for external blob values in robotinterface

[PeterBowman]

It is possible to externally (i.e. outside the XML robot configuration) override any parameters marked as extern-name with compound (lists) or simple (strings, integers...) values. This patch adds support for blobs, with unit testing (also covering external lists for completeness).

Use case: roboticslab-uc3m/yarp-devices#271 (comment).

[PeterBowman]

Windows builds are failing, I'm going to submit a fix soon.

[sonarqubecloud]

Quality Gate failed

Failed conditions

44.7% Coverage on New Code (required ≥ 80%)
26.5% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud

[PeterBowman]

Windows builds are failing, I'm going to submit a fix soon.

Fixed, there's nothing a double pointer can't do 😏.

[PeterBowman]

Should I rebase this and change the base branch to master according to the assigned milestone (YARP 3.10.0)?

[PeterBowman]

Hello. Is there any action I should perform here to clarify the intention of the PR or perhaps enhance the unit tests? Would it be possible to consider it for the 3.11.x release train (instead of 3.12 or later)?

[traversaro]

Hello. Is there any action I should perform here to clarify the intention of the PR or perhaps enhance the unit tests? Would it be possible to consider it for the 3.11.x release train (instead of 3.12 or later)?

fyi @randaz81