Fix file blocking issue with webcmdlets

[Claustn]

PR Summary

Resolve #7669.

Allows multiple uploads of the same file in parallel

This PR changes how -InFile parameter on the Web cmdlets open file handles. Previously the file was opened with ShareAccess None, meaning that the file was locked, resulting in that you, for instance, was not able to upload the same file to multiple destinations in parallel.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Change is not breaking
• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge and is not Work in Progress.
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• User-facing changes
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  • User-facing Documentation needed
    • Issue filed - Issue link:
• Testing - New and feature
  • Not Applicable or can only be tested interactively
  • OR
  • Make sure you've added a new test if existing tests do not effectively test the code changed
    • Add [feature] if the change is significant or affects feature tests

[iSazonov]

@Claustn Thanks! I slightly corrected the PR title and description.

[iSazonov]

@Claustn Please rename your commit - start title with [Feature] or add new empty commit with title [Feature] - this will run full test set.

[powercode]

LGTM!

[iSazonov]

CI Appveyor temporary failed.

[PaulHigin]

LGTM

[markekraus]

LGTM. My approval is pending successful completion of all [feature] tests.

[iSazonov]

@Claustn Thanks for discovering the issue and fixing it!