cmd/go: remove checks that all counters incremented are in counters.txt
This change removes cmd/go/testdata/counters.txt. It also removes the
code that prepares it and checks that it contains all registered
counters as well as counters for all flags and subcommands. It removes
the counter registration mechanism, and uses telemetry.NewCounter to
create new counters instead. It keeps the tests that check that at least
one counter is incremented if the go command is invoked in a script test.
Change-Id: Ic6bda5c64e90f0dd7e221968fce0e375e84d6e17
Cq-Include-Trybots: luci.golang.try:gotip-windows-amd64-longtest,gotip-linux-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/go/+/582715
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Sam Thanawalla <samthanawalla@google.com>