Update reflection metadata doc

[steveharter]

Summary

Addresses feedback from dotnet/runtime#76567 (comment). cc @jkotas, @jeffhandley

The reflection metadata doc is lacking and this PR helps, at least for the most common classes.

[opbld34]

Learn Build status updates of commit 86ba8bc:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/ns-System.Reflection.Metadata.Ecma335.xml	✅Succeeded	View
xml/ns-System.Reflection.Metadata.xml	✅Succeeded	View
xml/ns-System.Reflection.PortableExecutable.xml	✅Succeeded	View
xml/System.Reflection.Metadata.Ecma335/MetadataBuilder.xml	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[jkotas]

Thanks

[MSDN-WhiteKnight]

Consider expanding what low-level means here. For example, SRM is different from other libraries in that it could throw unmanaged access violation exceptions when using APIs on MetadataReader referring to disposed PeReader, instead of ObjectDisposedException. Not sure it's worth mentioning in namespace remarks, but it is very annoying in desktop apps, because on AV the whole process just dies with very poor error diagnostics.

[opbld34]

Learn Build status updates of commit 7620aa9:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/ns-System.Reflection.Metadata.Ecma335.xml	✅Succeeded	View
xml/ns-System.Reflection.Metadata.xml	✅Succeeded	View
xml/ns-System.Reflection.PortableExecutable.xml	✅Succeeded	View
xml/System.Reflection.Metadata.Ecma335/MetadataBuilder.xml	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel