Improve density of group context setting macros

Shared object binary size reduction:
x84_64           : 16112 bytes
ARM64            : 16008 bytes
ARM64(+Os)       : 21592 bytes
ARMv7(+Os+mthumb): 18480 bytes

Size reduction of symbols:
x84_64           : 15712 bytes
ARM64            : 18688 bytes
ARM64(+Os)       : 18404 bytes
ARMv7(+Os+mthumb): 17322 bytes

Compiles were done with clang version 18.1.8 and symbol sizes were
obtained using nm on the shared object.

Provides speed ups on older ARM64 cpus with very little impact on other
cpus.

Speedup:

c7i (skylake)
 Nature1080p      : x0.999
 Chimera          : x0.998

odroid C4
 Nature1080p      : x1.007
 Chimera          : x1.016
 Models1080p      : x1.005
 MountainBike1080p: x1.009
 Balloons1080p    : x1.008

Raspberry Pi 4
 Nature1080p      : x1.005
 Chimera          : x0.999
 Models1080p      : x0.999
 MountainBike1080p: x1.004
 Balloons1080p    : x1.003

Raspberry Pi 2 (Cortex-A7):
 (using size optimized build)
 Nature1080p      : x1.003
 Models1080p      : x0.997