Fix unsubstituted version/revision placeholders in version.h

[adityaanikam]

Fixes #3472.

getVersionString() and getGitRevision() in include/cutlass/version.h return the literal, unsubstituted CMake placeholder strings "@CUTLASS_VERSION@" / "@CUTLASS_REVISION@" for every consumer, since nothing in the current build ever processes version.h itself as a template.

The actual CMake-substituted revision is already available a few lines above: when built via CMake, CUTLASS_VERSIONS_GENERATED is defined and version_extended.h (generated from cmake/version_extended.h.in) redefines CUTLASS_REVISION with the real git hash; otherwise it falls back to "". getVersionBuild() already correctly reads CUTLASS_BUILD from that same mechanism — getGitRevision() just needs to do the same for CUTLASS_REVISION instead of hardcoding the placeholder.

There's no equivalent generated macro for the version string (the .in template only substitutes CUTLASS_VERSION_BUILD and CUTLASS_REVISION), so getVersionString() now builds a MAJOR.MINOR.PATCH[.BUILD] string from the existing getVersionMajor()/getVersionMinor()/getVersionPatch()/getVersionBuild() accessors instead.

Header-only change, no build system changes.