x/tools: document minimum requirements for tests #33986
Description
Some of the x/tools tests are resource intensive and doing go test golang.org/x/tools/... on a machine with low RAM may fail.
I think it'd be helpful to document the RAM requirement. That way, if the tests run out of memory on a machine that meets the minimum requirements, it becomes easy to determine that the problem lies with the tests and not the machine. The responsibility division is unclear when the requirements are unspecified.
This is similar to issue #19046 but for x/tools.
/cc @ianthehat @heschik @stamblerre @bradfitz