Fix not failing discovery when finding unsupported manifests

[SteveL-MSFT]

PR Summary

When DSC encounters a resource manifest it can't deserialize, it fails discovery completely. This was not intended. This can occur when we update the manifests with new fields that an older DSC does not understand. Instead, DSC should only support resources it can deserialize and emit info messages (so they don't show by default) for resources it can't use.

[Copilot]

Pull request overview

This PR adjusts DSC resource/extension discovery so that manifests that can’t be loaded/deserialized no longer cause discovery to fail; instead they are skipped and an info-level message is emitted (to avoid showing by default), improving forward/backward compatibility when manifest schemas evolve.

Changes:

• Skip (instead of failing) when load_manifest(...) errors during extension discovery; emit an info log with context.
• Downgrade some discovery failure logs to info and add localized failedLoadManifest messages.
• Add PowerShell tests asserting invalid manifests don’t break overall discovery and that an info message is produced.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
lib/dsc-lib/src/extensions/discover.rs	Handles load_manifest failures by logging at info and continuing.
lib/dsc-lib/src/discovery/mod.rs	Changes discovery-type failure logging from error to info.
lib/dsc-lib/src/discovery/command_discovery.rs	Logs manifest-load failures as localized info messages.
lib/dsc-lib/locales/en-us.toml	Adds failedLoadManifest localized strings for discovery and extension contexts.
dsc/tests/dsc_extension_discover.tests.ps1	Adds test ensuring invalid extension-discovered manifests don’t fail overall discovery.
dsc/tests/dsc_discovery.tests.ps1	Adds test ensuring invalid resource manifests generate an info message.

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