SCMP responder

[tzaeschke]

Add an SCMP responder feature.

[codecov]

Codecov Report

Attention: Patch coverage is 81.25000% with 15 lines in your changes are missing coverage. Please review.

Files	Coverage Δ	Complexity Δ
src/main/java/org/scion/jpan/Constants.java	100.00% <ø> (ø)	1.00 <0.00> (ø)
.../main/java/org/scion/jpan/internal/ScmpParser.java	85.71% <100.00%> (+12.24%)	7.00 <2.00> (ø)
...n/java/org/scion/jpan/AbstractDatagramChannel.java	84.21% <33.33%> (-0.35%)	77.00 <0.00> (ø)
src/main/java/org/scion/jpan/ScmpChannel.java	84.21% <93.75%> (+3.10%)	18.00 <3.00> (+3.00)
...ava/org/scion/jpan/internal/ScionHeaderParser.java	76.89% <62.96%> (-1.47%)	34.00 <4.00> (+4.00)	⬇️

... and 1 file with indirect coverage changes