Add dotnet_diagnostic.CA1859.severity = suggestion to editorconfig (PowerShell#25143)

Author: ArmaanMcleod

.editorconfig

@@ -119,6 +119,13 @@ csharp_prefer_simple_default_expression = true:suggestion
 
 dotnet_code_quality_unused_parameters = non_public:suggestion
 
+# Dotnet diagnostic settings:
+[*.cs]
+
+# CA1859: Use concrete types when possible for improved performance
+# https://learn.microsoft.com/en-gb/dotnet/fundamentals/code-analysis/quality-rules/ca1859
+dotnet_diagnostic.CA1859.severity = suggestion
+
 # CSharp code style settings:
 [*.cs]
 

build.psm1

@@ -11,7 +11,7 @@ param(
 # CI runs with PowerShell 5.0, so don't use features like ?: && ||
 Set-StrictMode -Version 3.0
 
-# On Unix paths is separated by colon
+# On Unix paths is separated by colon.
 # On Windows paths is separated by semicolon
 $script:TestModulePathSeparator = [System.IO.Path]::PathSeparator
 $script:Options = $null