Use built in sha1 for id generation

[nohwnd]

Description

Use built-in sha1 and slice for id generation.

Fix https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2050310
Fix microsoft/testfx#2762

[nohwnd]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[nohwnd]

@Evangelink You are a code owner here, but I am just changing the underlying implementation and no tests were changed, and I also checked that the produced trx from old and new mstest SDK produces the same guids, so all should be good.

[Evangelink]

@Evangelink You are a code owner here, but I am just changing the underlying implementation and no tests were changed, and I also checked that the produced trx from old and new mstest SDK produces the same guids, so all should be good.

I didn't know I was :D

Thanks for the PR! Looking forward for the perf improvement.