& background invocation operator should -WorkingDirectory when starting a job

[adityapatwardhan]

PR #10324 is merged and now we can use -WorkingDirectory when starting a job for background invocation operator.

The following code can be replaced:

PowerShell/src/System.Management.Automation/engine/runtime/Operations/MiscOps.cs

Lines 529 to 532 in f69f30b

	const string cmdPrefix = @"Microsoft.PowerShell.Management\Set-Location -LiteralPath $using:pwd ; ";
	// Minimize allocations by initializing the stringbuilder to the size of the source string + prefix + space for ${using:} * 2
	System.Text.StringBuilder updatedScriptblock = new System.Text.StringBuilder(cmdPrefix.Length + scriptblockBodyString.Length + 18);
	updatedScriptblock.Append(cmdPrefix);

Steps to reproduce

Expected behavior

Actual behavior

Environment data

Name                           Value
----                           -----
PSVersion                      7.0.0-daily.20190906
PSEdition                      Core
GitCommitId                    7.0.0-daily.20190906
OS                             Microsoft Windows 10.0.18978
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

[ayousuf23]

Please assign me to the issue. I submitted a PR for this issue (#16180).