libmath: use TVECHELPERS_STD_HASH macro for std::hash

Upstream Clang has enabled the -frelaxed-template-template-args option
by default (llvm.org/PR89807) and deprecated
-fno-relaxed-template-template-args. With the new relaxed
template-template behavior, libmath's partial specialization is also a
candidate for std::hash<std::string>
(i.e. std::hash<std::basic_string<char>> where VECTOR is
std::basic_string and T is char).

To avoid the ambiguity, use a C macro to define a partial
specialization for each of TVec{2,3,4}, TMat{22,33,44}, and
TQuaternion.

Bug: http://b/341084395
Test: atest hashcombine_test
Change-Id: I0837e0de327914f94a1dd13a49b470fc78e164b1