Pragmas before types and members get dropped when porting docs into triple slash comments

Start by reproducing the C# examples in the issue, including the pragma-wrapped Foo type and Utf8Formatter.Guid.cs. Trace the documentation-to-triple-slash-comment conversion for declarations and verify that conversion preserves every surrounding pragma line while adding the generated documentation comments.

When porting API docs into triple slash comments, classes that have #if def pragmas wrapped around their access modifiers lose the first line of the pragma.

Given the following example, The #if USEPUBLIC pragma line is dropped.

#if USEPUBLIC
    public
#else
    internal
#endif
    class Foo { }

Expected

    /// <summary>Foo summary</summary>
#if USEPUBLIC
    public
#else
    internal
#endif
    class Foo { }

Actual

    /// <summary>Foo summary</summary>
    public
#else
    internal
#endif
    class Foo { }

This occurs with other types of pragmas as well. An example from Utf8Formatter.Guid.cs shows a scenario of an #endregion getting dropped.

Before

namespace System.Buffers.Text
{
    public static partial class Utf8Formatter
    {
        #region Constants

        private const byte OpenBrace = (byte)'{';
        private const byte CloseBrace = (byte)'}';

        private const byte OpenParen = (byte)'(';
        private const byte CloseParen = (byte)')';

        private const byte Dash = (byte)'-';

        #endregion Constants

        /// <summary>
        /// Formats a Guid as a UTF8 string.
        /// </summary>
        /// <param name="value">Value to format</param>
        /// <param name="destination">Buffer to write the UTF8-formatted value to</param>
        /// <param name="bytesWritten">Receives the length of the formatted text in bytes</param>
        /// <param name="format">The standard format to use</param>
        /// <returns>
        /// true for success. "bytesWritten" contains the length of the formatted text in bytes.
        /// false if buffer was too short. Iteratively increase the size of the buffer and retry until it succeeds.
        /// </returns>
        /// <remarks>
        /// Formats supported:
        ///     D (default)     nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn
        ///     B               {nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn}
        ///     P               (nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn)
        ///     N               nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn
        /// </remarks>
        /// <exceptions>
        /// <cref>System.FormatException</cref> if the format is not valid for this data type.
        /// </exceptions>
        public static bool TryFormat(Guid value, Span<byte> destination, out int bytesWritten, StandardFormat format = default)

After

namespace System.Buffers.Text
{
    /// <summary>Provides static methods to format common data types as Utf8 strings.</summary>
    public static partial class Utf8Formatter
    {
        #region Constants

        private const byte OpenBrace = (byte)'{';
        private const byte CloseBrace = (byte)'}';

        private const byte OpenParen = (byte)'(';
        private const byte CloseParen = (byte)')';

        private const byte Dash = (byte)'-';

        /// <summary>Formats a <see cref="System.Guid" /> as a UTF8 string.</summary>
        /// <param name="value">The value to format.</param>
        /// <param name="destination">The buffer to write the UTF8-formatted value to.</param>
        /// <param name="bytesWritten">When the method returns, contains the length of the formatted text in bytes.</param>
        /// <param name="format">The standard format to use.</param>
        /// <returns><see langword="true" /> if the formatting operation succeeds; <see langword="false" /> if <paramref name="buffer" /> is too small.</returns>
        /// <remarks>Formats supported:
        /// |Format string|Result string|
        /// |--|--|
        /// |D (default)|nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn|
        /// |B|{nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn}|
        /// |P|(nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn)|
        /// |N|nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn|
        /// If the method fails, iteratively increase the size of the buffer and retry until it succeeds.</remarks>
        public static bool TryFormat(Guid value, Span<byte> destination, out int bytesWritten, StandardFormat format = default)