azpexpand command should not show StackTrace when there are template errors

[bryanbcook]

Exceptions should not propagate to end-users through public interfaces unless they are the result of uncaught issues in the application logic.

Expected:

c:\> gharun -W /pipelines/pipeline1.yml
The template is not valid.
(self)/pipeline1.yml: (Line: 28, Col: 1, Idx: 1024): While parsing a block mapping, did not find expected key.
c:\> $LASTEXITCODE
1

Actual:

c:\> gharun -W /pipelines/pipeline1.yml
<...log-contents...>
(self)/pipelines/pipeline1.yml: (Line: 28, Col: 1, Idx: 1042) - (Line: 28, Col: 6, Idx: 1047): While parsing a block mapping, did not find expected key.
Exception: The template is not valid. (self)/pipelines/pipeline1.yml: (Line: 28, Col: 1, Idx: 1042) - (Line: 28, Col: 6, Idx: 1047): While parsing a block mapping, did not find expected key.,    at GitHub.DistributedTask.ObjectTemplating.TemplateValidationErrors.Check() in /home/runner/work/runner.server/runner.server/src/Sdk/DTObjectTemplating/ObjectTemplating/TemplateValidationErrors.cs:line 88
   at AzureDevops.ReadTemplate(Context context, String filenameAndRef, Dictionary`2 cparameters, String schemaName) in /home/runner/work/runner.server/runner.server/src/Sdk/AzurePipelines/AzureDevops.cs:line 494
   at Runner.Client.Program.AzurePipelinesExpander.ExpandCurrentPipeline(Parameters handle, String currentFileName) in /home/runner/work/runner.server/runner.server/src/Runner.Client/Program.cs:line 828
   at Runner.Client.Program.<>c__DisplayClass29_2.<<Main>b__17>d.MoveNext() in /home/runner/work/runner.server/runner.server/src/Runner.Client/Program.cs:line 1710
c:\> $LASTEXITCODE
1

[ChristopherHX]

1. Hide Trace messages (to suppress the duplicated error) > move them to log file like in 277
2. Print Exception.Message instead of Exception.toString() so it doesn't include the exception name / stacktrace.

The template is not valid. wouldn't be followed by a newline, but otherwise pretty similar otherwise.

Seems like the template errors from the yaml parser has an idx field, which my current exception regex wouldn't support..