This commit replaces synchronized blocks and methods
that are used frequently or that guard blocking I/O
operations with locks. This is required to prevent
virtual threads pinning, as explained in JEP 444 [1].
Note that synchronized blocks and methods that are used
infrequently (like AutomaticJobRegistrar#start/stop) or
that guard in-memory operations were not replaced as this
is not required, see JEP 444 [1].
Resolves to #4399
---
[1]: https://openjdk.org/jeps/444
5bccfed523