[HLSL] Add validation for the -enable-16bit-types option (#85340)

Previously, the clang compiler with the dxc driver would accept the
-enable-16bit-types flag without checking to see if the required
conditions are met for proper processing of the flag.
Specifically, -enable-16bit-types requires a shader model of at least
6.2 and an HLSL version of at least 2021.
This PR adds a validation check for these other options having the
required values, and emits an error if these constraints are not met.
Fixes #57876

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Co-authored-by: Damyan Pepper <damyanp@microsoft.com>
Co-authored-by: Chris B <cbieneman@microsoft.com>