test: Streamline test suite a little

This change aims to streamline the integrationtest suite and reduce friction when running (parts of) test suites.

Changes:
- add `test-testname` to makefile to easily run one suite
- made skipping tests first class citizen in test.sh (all available testsuites and the reasons they are skipped are now better exposed and discovered)
- suppress some output of gotest unless there is an error
- no longer build binary for examples and gotest suites
- removed .SILENT from makefile as it being applied to only some targets makes it feel weird (I just learned about this option btw, feel free to comment on this change)
- move individual tests out of `test.sh` and into `test-misc.sh`
- introduced the concept of testsuites to `test.sh`

test/test-misc.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+# simple tests that don't deserve their own testfile
+
+# library of utility functions
+# shellcheck disable=SC1091
+. test/util.sh
+
+echo running "$0"
+
+ROOT=$(dirname "${BASH_SOURCE}")/..
+cd "${ROOT}" || exit 1
+
+failures=''
+
+# ensure there is no trailing whitespace or other whitespace errors
+run-test git diff-tree --check $(git hash-object -t tree /dev/null) HEAD
+
+# ensure entries to authors file are sorted
+start=$(($(grep -n '^[[:space:]]*$' AUTHORS | awk -F ':' '{print $1}' | head -1) + 1))
+run-test diff <(tail -n +$start AUTHORS | sort) <(tail -n +$start AUTHORS)
+
+if [[ -n "$failures" ]]; then
+	echo 'FAIL'
+	echo "The following tests have failed:"
+	echo -e "$failures"
+	echo
+	exit 1
+fi
+echo 'PASS'