Investigate test failures related to SDKs located on paths containing spaces on Windows

[bkonyi]

This issue originally surfaced after this CL landed and was tracked in dart-lang/sdk#59784, assuming the failure was caused by the related CL.

After some digging, it turns out that the webdev tests can make a copy of the SDK under the temp directory for use in tests. This directory name was prefixed with sdk copy. Logging landed by @a-siva indicated that webdev/test/e2e_test.dart was failing with the following message:

C:\src\temp\sdk is not an AOT snapshot, it cannot be run with 'dartaotruntime'

Changing the copied SDK directory name prefix to sdk_copy resolved the issue, implying that paths with spaces aren't being handled properly somewhere in the pipeline.

[bkonyi]

This appears to actually be a VM issue, so there's nothing to do here in webdev.