Reject illegal paths in OSC 9;9

[DHowett]

closes #12378

[DHowett]

There is an open question as to whether we should do this here, reject the path outright, or do it in every place that uses the path.

• Accepting the path with sanitization will result in invalid paths being passed through outright and later failures (when those paths fail to exist.)
• Rejecting the path is probably the safest option. Should I do that instead?
• We could make this part of the OSC 9;9 state machine, but that's a lot more work and doing so may result in behavior inconsistent from that of ConEmu
• Doing it everywhere that uses a path (including session save/restore) would probably result in us forgetting someplace.

[DHowett]

@msftbot merge this in 1 minute

[ghost]

Hello @DHowett!

Because you've given me some instructions on how to help merge this pull request, I'll be modifying my merge approach. Here's how I understand your requirements for merging this pull request:

• I won't merge this pull request until after the UTC date Tue, 27 Sep 2022 22:56:45 GMT, which is in 1 minute

If this doesn't seem right to you, you can tell me to cancel these instructions and use the auto-merge policy that has been configured for this repository. Try telling me "forget everything I just told you".

[DHowett]

Tests passed in an earlier rev (and the only changes are formatting.)

[ghost]

🎉Windows Terminal v1.15.2874 has been released which incorporates this pull request.:tada:

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[ghost]

🎉Windows Terminal Preview v1.16.3463.0 and v1.16.3464.0 has been released which incorporates this pull request.:tada:

Handy links:

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