Consider supporting #pragma pack_matrix()

[chaoticbob]

To make shader porting from HLSL to Slang easier, consider supporting the #pragma pack_matrix() directive. Currently slangc issues a warning and ignores the directive. Support this directive could save someone from having to painstakingly go through their shader code base and decorating their matrices with either row_major or column_major.

[ArielG-NV]

For now to achieve the same functionality the following compile options can be used:
-matrix-layout-row-major and -matrix-layout-column-major