freedreno/ir3: Don't leave holes the UBO upload plan.

freedreno/ir3: Don't leave holes the UBO upload plan.

Shaders may not use a particular region of a UBO in a given shader (think
UBOs shared between stages, or between shaders), and by just always
extending the existing range for a given UBO, we'd waste bandwidth
uploading it, and also waste our precious const space in storing the
unused data.

Instead, only upload exactly the ranges we can use, and merge ranges when
they're neighbors.  We may end up with more upload packets, but the
bandwidth savings is surely going to be worth it (and if find we want a
distance threshold for merging with nearby uploads, that would be easy to
add).

total instructions in shared programs: 9266114 -> 9255092 (-0.12%)
total full in shared programs: 343162 -> 341709 (-0.42%)
total constlen in shared programs: 1454368 -> 1275236 (-12.32%)
total cat6 in shared programs: 93073 -> 82589 (-11.26%)
total (ss) in shared programs: 212402 -> 206404 (-2.82%)
total (sy) in shared programs: 122905 -> 114007 (-7.24%)

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7036>