String compression on intrinsics x86 and x86_64

String compression on intrinsics x86 and x86_64

Changes on intrinsics and Code Generation (x86 and x86_64)
for string compression feature. Currently the feature is off.

The size of boot.oat and boot.art for x86 before and after the
changes (feature OFF) are still. When the feature ON,
boot.oat increased by 0.83% and boot.art decreased by 19.32%.

Meanwhile for x86_64, size of boot.oat and boot.art before and
after changes (feature OFF) are still. When the feature ON,
boot.oat increased by 0.87% and boot.art decreased by 6.59%.

Turn feature on: runtime/mirror/string.h (kUseStringCompression = true)
runtime/asm_support.h (STRING_COMPRESSION_FEATURE 1)

Test: m -j31 test-art-host
All tests passed both when the mirror::kUseStringCompression
is ON and OFF.

The jni_internal_test changed to assert an empty string length
to be equal -(1 << 31) as it is compressed.

Bug: 31040547
Change-Id: Ia447c9b147cabb6a69e6ded86be1fe0c46d9638d