* ethclient/gethclient: improve time-sensitive flaky test
* eth/catalyst: fix (?) flaky test
* core: stop blockchains in tests after use
* core: fix dangling blockchain instances
* core: rm whitespace
* eth/gasprice, eth/tracers, consensus/clique: stop dangling blockchains in tests
* all: address review concerns
* core: goimports
* eth/catalyst: fix another time-sensitive test
* consensus/clique: add snapshot test run function
* core: rename stop() to stopWithoutSaving()
Co-authored-by: Felix Lange <fjl@twurst.com>