docs/system/arm/emulation.rst: Add missing implemented features

docs/system/arm/emulation.rst: Add missing implemented features

As of version DDI0487K.a of the Arm ARM, some architectural features
which previously didn't have official names have been named.  Add
these to the list of features which QEMU's TCG emulation supports.
Mostly these are features which we thought of as part of baseline 8.0
support.  For SVE and SVE2, the names have been brought into line
with the FEAT_* naming convention of other extensions, and some
sub-components split into separate FEAT_ items.  In a few cases (eg
FEAT_CCIDX, FEAT_DPB2) the omission from our list was just an oversight.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240418152004.2106516-2-peter.maydell@linaro.org