[3/11][Clang][RISCV] Expand all variants for unit stride segment load

This is the 3rd patch of the patch-set. For the cover letter, please
checkout D152069.

Depends on D152070.

This patch expands all variants of unit stride segment load, including
the policy variants. This patch also fixes the trailing suffix in the
intrinsics' function name that representing the return type, adding
`x{NF}`.

Currently the tuple type co-exists with the non-tuple type intrinsics.
Since the co-existance is temporary, this patch only adds test cases of
all variants for vlseg2e32 to show the capability done.

Test cases of other data type and NF will be added in the patch-set
when the replacement happens.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D152071