testsuite: Pass -ki128k -kc128k for performance tests

Setting a larger stack (chunk size/ initial) gives a greater protection from stack underflow (which allocates more stack chunks). This stabilises some tests against differences cause by more things being pushed onto the stack.

The performance tests are generally testing work done by the compiler, using allocation as a proxy, so removing/stabilising the allocations due to the stack gives us more stable tests which are also more sensitive to actual changes in compiler performance.

Fixes #23439 (closed)