Add tests for @time compilation reporting

[IanButterworth]

These tests are based off the examples in SnoopCompile's manual https://timholy.github.io/SnoopCompile.jl/stable/snoopr/

[IanButterworth]

@vtjnash I'd appreciate a 2nd set of eyes on this, especially the stdout capture test macro

[vtjnash]

Pipe, and especially readavailable, are not reliable or safe to use for capturing stdout

[vtjnash]

Is this something supported by @test_warn?

[IanButterworth]

Is this something supported by @test_warn?

Unfortunately not because @time outputs to stdout. Perhaps there should be @test_stdout and @test_stderr, and @test_warn could be an alias for the latter?

[IanButterworth]

How about using a file? (pushed)

[IanButterworth]

bump @vtjnash

[vtjnash]

yeah, an IOStream should be fine, but let's use mktemp so it gets cleaned up immediately too