[WIP] experiment - Use SemaphoreSlim to prevent concurrent basestream access

[Numpsy]

A spin off / follow up to #589 which tries to use SemaphoreSlim to prevent concurrent access to the base stream instead of lock()

Another followup thought after looking at the bits that lock a bit more:

The TestArchive function:

1. calls TestLocalHeader, which locks the stream for the duration of the operation
2. reads the stream content via GetInputStream, which returns the locking PartialInputStream
3. uses ZipHelperStream to read the data descriptor, which I don't think does any locking

so might (3) be a hole where multiple things could read the stream at once?

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[codecov[bot]]

Codecov Report

Merging #619 (215f747) into master (1b9fcfc) will increase coverage by 0.05%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #619      +/-   ##
==========================================
+ Coverage   73.35%   73.40%   +0.05%     
==========================================
  Files          68       68              
  Lines        8718     8735      +17     
==========================================
+ Hits         6395     6412      +17     
  Misses       2323     2323              

Impacted Files	Coverage Δ
src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs	78.06% <100.00%> (+0.25%)	:arrow_up:

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[Numpsy]

I've read elsewhere that you don't need to dispose the semaphore if you aren't using it's wait handle property directly, but I don't know if that's something to depend on.

Extra related question: Should the Async stream calls use ConfigureAwait ?

[piksel]

Regarding ConfigureAwait:

if you’re writing general-purpose library code, use ConfigureAwait(false)

from https://devblogs.microsoft.com/dotnet/configureawait-faq/#when-should-i-use-configureawaitfalse

[Numpsy]

Yes, just thought i'd check as it can mean adding it in many places, and #574 didn't seem to do it.

[piksel]

No, but that's just my bad 😅