Optimize arraycopy with constant copy size

Optimize arraycopy sequence if copy size is constant
and less than or equal to 64 bytes. This feature can
be disabled by env variable
TR_DisableArrayCopyInlineSmallSizeConstantCopySize.

Create generateMemoryCopyInstructions that loads and stores
memory based on specified register size. This method is used
by multiple arraycopy inline methods to reduce the repetition
of the same code.

Update generateArrayElement{Load|Store} to include
vector registers and instructions.

Signed-off-by: Annabelle Huo <[email protected]>