Replace invoke kind kDexCacheViaMethod with kRuntimeCall.

In preparation for replacing the dex cache method array
with a hash-based array, get rid of one unnecessary use.
This method load kind is currently used only on mips for
irreducible loops and OSR, so this should have no impact
on x86/x86-64/arm/arm64.

Test: m test-art-host-gtest
Test: testrunner.py --host
Test: Repeat the above tests with manually changing
      kDexCachePcRelative to kRuntimeCall in sharpening.cc.
      (Ignore failures in 552-checker-sharpening.)
Bug: 30627598
Change-Id: Ifce42645f2dcc350bbb88c2f4642e88fc5f98152