### Description
<!-- Describe your changes. -->
Update to .net8. Didn't want to build with the latest VS2022 using net6
(which was EOL last year).
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
### Description
<!-- Describe your changes. -->
- fix issue with handling string input
- set minSdkVersion
- otherwise defaults to 19 which we don't support and the build breaks
- comment out the debug logging hook
- enabling it breaks the Android native logging
- can be enabled if you need to debug C# code
- update test data tools to allow creating input data for raw file
contents (e.g. audio) and from strings (e.g. auth token value)
- fix some warnings
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
Improve test setup
### Description
<!-- Describe your changes. -->
Comment out ORT-Nightly feed in NuGet.config to see if that makes the
Secure Supply Chain Analysis CI step happy.
Add info to readme on manually adding feed and using it.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
### Description
<!-- Describe your changes. -->
MAUI test app with tooling to add model and generated or provided input
test data.
The app will load the model and validate the output. It can also run a
specified number of iterations to provide basic performance information.
<img width="401" alt="image"
src="https://github.com/microsoft/onnxruntime/assets/979079/daf3af13-fb22-4cbb-9159-486b483a7485">
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
Primarily to make it easier to test an arbitrary model on iOS. A MAUI
app allows testing on all platforms.
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Co-authored-by: Edward Chen <18449977+edgchen1@users.noreply.github.com>
