Removed ${aspnet-request-posted-body} because not threadsafe

[snakefoot]

NLog 5.0 only supports threadsafe layoutrenderers. This LayoutRenderer modifies the Body-Stream while reading, so it gives unwanted side-effects and unexpected errors. See also #753

Instead request-body should be explicitly captured using the middleware-pipeline. And maybe stored in HttpContext.Items or in ScopeContext-Property.

[codecov-commenter]

Codecov Report

Merging #754 (473b356) into master (d85dfab) will increase coverage by 1%.
The diff coverage is n/a.

❗ Current head 473b356 differs from pull request most recent head 998710d. Consider uploading reports for the commit 998710d to get more accurate results

@@          Coverage Diff          @@
##           master   #754   +/-   ##
=====================================
+ Coverage      63%    64%   +1%     
=====================================
  Files          49     48    -1     
  Lines         834    779   -55     
  Branches      206    193   -13     
=====================================
- Hits          522    497   -25     
+ Misses        238    214   -24     
+ Partials       74     68    -6     

Impacted Files	Coverage Δ
...utRenderers/AspNetRequestDurationLayoutRenderer.cs	58% <0%> (+2%)	⬆️

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[sonarqubecloud]

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[snakefoot]

Thanks to @bakgerman now NLog.Web.AspNetCore v5.1 re-introduces ${aspnet-request-posted-body} with help from middleware:

app.UseMiddleware<NLog.Web.NLogRequestPostedBodyMiddleware>();

It is no longer necessary to explicit call context.Request.EnableBuffering(); as it is handled by the middleware.