The threee tags `<name>`, `</name>` and `<command>` were frequently used
with a leading space that this removes. The reason this habbit is so
widespread in testcases is probably that they have been copy and pasted.
Hence, fixing them all now might curb this practice from now on.
Closes#12028
These are ones likely to fail on heavily-loaded machines that alter the
normal test timing. Most of these tests already had the flaky keyword
since this condition makes them more likely to fail on CI.
Added Curl_resolver_kill() for all three resolver modes, which only
blocks when necessary, along with test 1592 to confirm
curl_multi_remove_handle() doesn't block unless it must.
Closes#3428Fixes#3371
