Add method info to oat files

The method info data is stored separately from the code info to
reduce oat size by improving deduplication of stack maps.

To reduce code size, this moves the invoke info and inline info
method indices to this table.

Oat size for a large app (arm64): 77746816 -> 74023552 (-4.8%)
Average oat size reduction for golem (arm64): 2%

Repurposed unused SrcMapElem deduping to be for MethodInfo.
TODO: Delete SrcMapElem in a follow up CL.

Bug: 36124906

Test: clean-oat-host && test-art-host-run-test

Change-Id: I2241362e728389030b959f42161ce817cf6e2009