* Update TFM to net6.0

* Exclude test projects from source-build

* Remove net472 TFM

* Use property instead of hardcoded version

* EscapeUriString is obsolete.  Change to EscapeDataString

* Revert "EscapeUriString is obsolete.  Change to EscapeDataString"

This reverts commit e38710b.

* Add NoWarn for SYSLIB0013

Don't warn on SYSLIB0013 - Uri.EscapeUriString() is obsolete.
This is marked obsolete for net6.0 and changing it to
Uri.EscapeDataString() changes behavior.  Ignore the warning.

* Update build tasks to fully qualify base class

Because of the update to net6, implicit namespace support
is causing a conflict  when using Task as a base class.

* Fix one too aggressive search/replace

…7814)

Update to an SDK that understands NUGET_ENABLE_EXPERIMENTAL_HTTP_RETRY, and set some values in common entry points (validated in binlogs)

Users who need these values set from non-arcade execution paths can set them globally via yaml or their own scripts.

Follow-up for #7814

…827.11 (#7810)

[main] Update dependencies from dotnet/roslyn

…/linker (#7816)

[main] Update dependencies from dotnet/xliff-tasks dotnet/arcade mono/linker