cmd/go: convert tests using testdata files to script framework

[matloob]

I'd like to convert the cmd/go tests using testdata/src as their GOPATH to the script framework. We don't run those tests in parallel because we don't want concurrent go command runs started by the tests using the same GOPATH. While we can modify the test framework to copy the testdata files to a isolated temp directory GOPATH for those tests, I think it's simpler to just convert those tests to the script framework, and that has the additional benefit that we keep the test logic and data together in the same files making the tests easier to read.

[gopherbot]

Change https://golang.org/cl/212877 mentions this issue: cmd/go: convert TestIssue17119 to the script test framework

[gopherbot]

Change https://golang.org/cl/212878 mentions this issue: cmd/go: convert TestGoGenerateBadImports to script framework

[gopherbot]

Change https://golang.org/cl/212879 mentions this issue: cmd/go: convert TestRunPkg to the script framework

[gopherbot]

Change https://golang.org/cl/212811 mentions this issue: cmd/go: convert TestCoverageImportMainLoop and TestGoTestMain

[gopherbot]

Change https://golang.org/cl/212812 mentions this issue: cmd/go: convert TestGoBuildNotMain to script framework

[gopherbot]

Change https://golang.org/cl/212813 mentions this issue: cmd/go: convert TestIssue7108 to the script framework

[gopherbot]

Change https://golang.org/cl/212814 mentions this issue: cmd/go: convert TestRunInternal to the script test framework

[gopherbot]

Change https://golang.org/cl/212815 mentions this issue: cmd/go: convert TestCoveragePattern to the script framework

[gopherbot]

Change https://golang.org/cl/212816 mentions this issue: cmd/go: convert tests using testdata/src/syntaxerror to scripts

[gopherbot]

Change https://golang.org/cl/212937 mentions this issue: cmd/go: convert TestGoTestDetectsTestOnlyImportCycles to script

[gopherbot]

Change https://golang.org/cl/212939 mentions this issue: cmd/go: convert TestGoTestImportErrorStack to the script framework

[gopherbot]

Change https://golang.org/cl/213126 mentions this issue: cmd/go: convert TestListTests to the script framework