* go.mod: update golang.org/x/tools to v0.1.8
Fixes TestGeneratedDoc on go1.18
* TeamCity: bump test matrix
Add 1.18 to test matrix. Remove 1.15 from test matrix and from support range.
* proc,tests: update for regabi on arm64 and 386
Make sure that stacktrace registers always contain the PC register of
the current frame, even though the debug_frame rules might not specify
it on architectures that use a link register.
The PC register is needed to look up loclist entries for variable
evaluation.
* goversion: bump maximum supported Go version to 1.18
* proc: disable asyncpreempt on linux/arm64
Asyncpreempt on linux/arm64 can sometimes restart a sequence of
instructions which will make breakpoint appear to be hit twice in some
cases.