properly enumerate uninstrumented bounds

[max-charlamb]

partial fix for #119921.

• Updates EnumMemoryRegions to account for uninstrumented bounds added by Walk compressed IL -> Native map for EventTrace and stacktrace symbolication scenarios #116031
• Adds padding to end of enumerated DebugInfo stream. This accounts for the nibblereader reading in data in platform pointer sized increments. Previously, if the debuginfo was not aligned the last read would end up partially failing.

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Pull Request Overview

This PR fixes the enumeration of memory regions for debug information by properly handling uninstrumented bounds that were introduced in a previous change. The fix ensures that both instrumented and uninstrumented bounds are correctly accounted for when enumerating memory regions, and adds proper alignment padding to prevent partial read failures.

Key Changes:

• Updates memory region enumeration to handle uninstrumented bounds alongside existing instrumented bounds
• Adds alignment padding to prevent NibbleReader from partially failing on unaligned debug info streams

[noahfalk]

👍

[steveisok]

/backport to release/10.0

[github-actions]

Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17990332541