util: Add util functionality for GL4.1 support

util: Add util functionality for GL4.1 support

This patch adds the following tgsi utilities

* tgsi_dynamic_indexing: This utility flattens out the dyanamic indexing of constant buffers
* tgsi_vpos: This utility writes zeros to position at index 0 in vertex shader.
  This utility can be used if there is no shader output in vertex shader
* util_make_tess_ctrl_passthrough_shader: This adds passthough tessellation control shader.
  Input of passthrough tess ctrl shader is output of vertex shader
  and output is input of tessellation eval shader.
  If program has tessellation eval shader but no tessellation control shader,
  this utility can be used to create passthrough tessellation control shader.

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Charmaine Lee <charmainel@vmware.com>
Signed-off-by: Neha Bhende <bhenden@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5317>