docs: add XML documentation for CMS CompressedData stream parser (Batch 15f)

[KonradSop]

Description

Adds XML documentation to CmsCompressedDataParser — the streaming read-side counterpart to
CmsCompressedData (Batch 15d):

• Class summary — streaming decompress workflow via GetContent().
• Remarks — lazy compressed-content draining, stream disposal, buffering guidance, and a C# example.
• Constructors — byte array and stream overloads; ArgumentNullException and CmsException on the
  stream constructor.
• GetContent — returns a typed stream over the decompressed content; CmsException when reading fails.

Legacy /** block comments converted to XML.

Key Accomplishments

• Streaming compressed-data discoverability: IDE tooltips now cover the parser surface.
• Accurate exception contracts: documented only where the implementation throws.
• Focused scope: single file; no behavioural or signature changes.
• Documentation quality: all new or modified XML documentation lines are at most 120 characters.

Verification

• Build Status: dotnet build crypto/src/BouncyCastle.Crypto.csproj -c Release — 0 errors, no new warnings.
• Scope: Documentation-only; no behavioural or signature changes.

Checklist before requesting a review

• I have performed a self-review of my code
• I have kept the patch limited to only change the parts related to the patch
• This change requires a documentation update

See also Contributing Guidelines.