[1.20.6] 3.15.9

Commits in Release 3.15.9:

chore(config-core): lift up logic for serializeOneTo
chore(config-core): lift up logic for loadFromJson and writeTo
fix(config-core): write comments and name in writeTo, not serializeOneTo
fix(translate): do not pretend there is a page source if the connection fails
fix(translate): correct url in testmod
fix(translate): strange workaround
chore(translate): more text for workaround
chore(translate): comment out workaround again since google might have just been flaky
style: make variant names common

LibJF