The coordinator has some custom logic for "go_test:*" dist test names
involved in partitioning, merging, and sorting them using historical
test timing data. We also have many builder-specific dist test adjust
policies, and some parts of them have become out of date (e.g.,
macTestPolicy skips "wiki", a dist test that's long gone).

Go 1.21 is simplifying the naming pattern for dist test names, and
we want to do that without having to manually update the (many!)
existing adjust policies, as well as to avoid breaking or creating
a need to re-engineer the existing mechanisms that make "go_test:*"
dist test names special.

Make that possible by remapping the 'go tool dist test -list' output
from the new "pkg[:variant]" format to the previous format (or pass it
through unmodified if it's already in the old format) for the purpose
of dist test adjust policies only. Also keep the raw unmodified dist
test name around since it's needed for invoking said dist tests.

For golang/go#37486.
For golang/go#59990.

Change-Id: Ie958609de2a810fa0053a00091a0c54c3f8bfd83
Reviewed-on: https://go-review.googlesource.com/c/build/+/496190
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Austin Clements <austin@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>

The work to add the -json flag to the 'dist test' command also cleaned
how dist tests are tracked and registered. By now, a pair of (import
path, variant) strings is sufficient to uniquely identify every dist
test that exists. Some of the custom dist test names have been improved
along the way. And since the names are already changing a little anyway,
we use this opportunity to make them more uniform and predictable.

The mapping from the old dist test names to the new is as follows:

- "go_test:pkg"       → "pkg"  (this is the most common case)
- "go_test_bench:pkg" → "pkg:racebench"
- all other custom names are now called "pkg:variant", where variant
  is a description of their test configuration and pkg is the import
  path of the Go package under test

CL 495016 introduced test variants and used variant names for rewriting
the Package field in JSON events, and now that same name starts to also
be used as the dist test name.

Like previously done in CL 494496, registering a test variant involving
multiple Go packages creates a "pkg:variant" dist test name for each.
In the future we may combine their 'go test' invocation purely as an
optimization.

We can do this with the support of CL 496190 that keeps the coordinator
happy and capable of working with both new and old names.

In the end, all dist tests now have a consistent "pkg[:variant]" name.

For #37486.
For #59990.

Change-Id: I7eb02a42792a9831a2f3eeab583ff635d24269e8
Co-authored-by: Austin Clements <austin@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/496181
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

It worked in https://ci.chromium.org/b/8780270441624243121!
Turn it on everywhere as the next step.

For golang/go#59990.

Change-Id: I341c86f49b41c6784b19ce546814c8d359e26e57
Reviewed-on: https://go-review.googlesource.com/c/build/+/497695
TryBot-Bypass: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>

The experiment has graduated to default behavior in crrev.com/c/4558786
and can be removed here. (This undoes the change applied in CL 497695.)

For golang/go#59990.

Change-Id: Ie49407efbcb2641a61ad992e2443e6bd30057730
Reviewed-on: https://go-review.googlesource.com/c/build/+/499681
TryBot-Bypass: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>