build(repo): wire HTTP-Tests and Tests-Agents into the solution

Restore the MTConnect.NET-Tests-Agents and MTConnect.NET-HTTP-Tests
project entries to MTConnect.NET.sln, their build configurations for
all four solution-wide configurations, and their SolutionFolders mapping
under "Tests". Both projects were dropped from the solution in
c6ac2bc (docs-gen) so dotnet build/test against the solution file no
longer enumerates them; running tests against the project directories
directly still worked but the solution-level CI sweep missed all 15
HTTP-Tests fixtures.

Author: ottobolyos

MTConnect.NET.sln

@@ -137,6 +137,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MTConnect.NET-Docs-Tests",
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MTConnect.NET-DocsGen", "build\MTConnect.NET-DocsGen\MTConnect.NET-DocsGen.csproj", "{17E64F59-0E62-4FCE-BEC4-EABBCF95B9A2}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MTConnect.NET-Tests-Agents", "tests\MTConnect.NET-Tests-Agents\MTConnect.NET-Tests-Agents.csproj", "{AE09D1CA-5572-40BF-B984-74230E8634E1}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MTConnect.NET-HTTP-Tests", "tests\MTConnect.NET-HTTP-Tests\MTConnect.NET-HTTP-Tests.csproj", "{3E89B860-A428-470C-8E48-0DDABC4027F0}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -489,6 +493,22 @@ Global
 		{17E64F59-0E62-4FCE-BEC4-EABBCF95B9A2}.Package|Any CPU.Build.0 = Debug|Any CPU
 		{17E64F59-0E62-4FCE-BEC4-EABBCF95B9A2}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{17E64F59-0E62-4FCE-BEC4-EABBCF95B9A2}.Release|Any CPU.Build.0 = Release|Any CPU
+		{AE09D1CA-5572-40BF-B984-74230E8634E1}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{AE09D1CA-5572-40BF-B984-74230E8634E1}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{AE09D1CA-5572-40BF-B984-74230E8634E1}.Docker|Any CPU.ActiveCfg = Debug|Any CPU
+		{AE09D1CA-5572-40BF-B984-74230E8634E1}.Docker|Any CPU.Build.0 = Debug|Any CPU
+		{AE09D1CA-5572-40BF-B984-74230E8634E1}.Package|Any CPU.ActiveCfg = Debug|Any CPU
+		{AE09D1CA-5572-40BF-B984-74230E8634E1}.Package|Any CPU.Build.0 = Debug|Any CPU
+		{AE09D1CA-5572-40BF-B984-74230E8634E1}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{AE09D1CA-5572-40BF-B984-74230E8634E1}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3E89B860-A428-470C-8E48-0DDABC4027F0}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3E89B860-A428-470C-8E48-0DDABC4027F0}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3E89B860-A428-470C-8E48-0DDABC4027F0}.Docker|Any CPU.ActiveCfg = Debug|Any CPU
+		{3E89B860-A428-470C-8E48-0DDABC4027F0}.Docker|Any CPU.Build.0 = Debug|Any CPU
+		{3E89B860-A428-470C-8E48-0DDABC4027F0}.Package|Any CPU.ActiveCfg = Debug|Any CPU
+		{3E89B860-A428-470C-8E48-0DDABC4027F0}.Package|Any CPU.Build.0 = Debug|Any CPU
+		{3E89B860-A428-470C-8E48-0DDABC4027F0}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3E89B860-A428-470C-8E48-0DDABC4027F0}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -543,6 +563,8 @@ Global
 		{E726EF85-4464-47D9-91EF-AD435D14F9D6} = {14375E03-6BF8-45E6-B868-D2399368992B}
 		{B340EB29-41C8-4C64-859F-387D51F401A5} = {14375E03-6BF8-45E6-B868-D2399368992B}
 		{17E64F59-0E62-4FCE-BEC4-EABBCF95B9A2} = {BBF53739-168D-4635-8595-083AC0C65E4C}
+		{AE09D1CA-5572-40BF-B984-74230E8634E1} = {14375E03-6BF8-45E6-B868-D2399368992B}
+		{3E89B860-A428-470C-8E48-0DDABC4027F0} = {14375E03-6BF8-45E6-B868-D2399368992B}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {CC13D3AD-18BF-4695-AB2A-087EF0885B20}