mesa/texgetimage: use master conversion function in get_tex_rgba_uncompressed()

Updates get_tex_rgba_uncompressed() to use always use the master
conversion function.

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Eduardo Lima Mitev <elima@igalia.com>
mesa: Unify rebase logic for glReadPixels and glGetTexImage.

Both glReadPixels and glGetTexImage have RGBA rebasing logic that is almost
the same, so move that logic to a separate helper function
_mesa_get_rebase_format_for_color_read_back and call this from
both implementations.
mesa: Replace _mesa_unpack_bitmap with _mesa_unpack_image()

_mesa_unpack_bitmap() was introduced by commit 02b801c to handle the case
when data is stored in PBO by display lists, in the context of this bug:

Incorrect pixels read back if draw bitmap texture through Display list
https://bugs.freedesktop.org/show_bug.cgi?id=10370

Since _mesa_unpack_image() already handles the case of GL_BITMAP, this patch
removes _mesa_unpack_bitmap() and makes affected calls go through
_mesa_unapck_image() instead.

The sample test attached to the original bug report passes with this change
and there are no piglit regressions.

Signed-off-by: Eduardo Lima Mitev <elima@igalia.com>
mesa: Remove _mesa_unpack_color_span_uint

This is no longer used.
mesa: Remove _mesa_make_temp_ubyte_image

Now that we have _mesa_format_convert we don't need this.

texstore_rgba will use the GL_COLOR_INDEX to RGBA conversion
helpers instead and compressed formats that used
_mesa_make_temp_ubyte_image to create an ubyte RGBA temporary
image can call _mesa_texstore with a RGBA/ubyte dst to
achieve the same goal.
mesa: Remove _mesa_make_temp_float_image

Now that we have _mesa_format_convert we don't need this.

This was only used to create temporary RGBA float images in the process
of storing some compressed formats. These can call _mesa_texstore
with a RGBA/float dst to achieve the same goal.
mesa: Remove _mesa_unpack_color_span_ubyte

This is no longer used anywhere after moving to _mesa_format_convert.
mesa: Remove (signed) integer pack and span functions.

These are no longer used now that we moved to _mesa_format_convert.
swrast: Replace _mesa_unpack_color_span_float with _mesa_format_convert
swrast: Remove unused variable.
mesa: Remove _mesa_unpack_color_span_float

And various helper functions that went unused after removing it.
mesa: Replace _mesa_pack_rgba_span_float with _mesa_format_convert
mesa: Remove _mesa_pack_rgba_span_float and tmp_pack.h

_mesa_pack_rgba_span_float was the last of the color span functions
and we have replaced all calls to it with calls to _mesa_format_convert,
so we can remove it together with tmp_pack.h which was used to
generate the pack functions for various types that wer used from
the various color span functions that have been removed.
mesa: Remove _mesa_(un)pack_index_span

These are not used anywhere.