[llvm] [GlobalISel] Optimize ULEB128 usage (PR #90565)

[Amara Emerson via llvm-commits]

aemerson wrote:

Again ClamAV is missing from these results, but the other benchmarks show a very nice improvement! Thanks for doing this.

```
Program                                       compile_time
                                              lhs          rhs    diff
sqlite3/sqlite3                                 2.49         2.49 -0.1%
SPASS/SPASS                                     4.57         4.56 -0.2%
mafft/pairlocalalign                            2.68         2.68 -0.2%
consumer-typeset/consumer-typeset               3.59         3.59 -0.2%
lencod/lencod                                   4.66         4.65 -0.2%
Bullet/bullet                                  11.02        11.00 -0.2%
kimwitu++/kc                                    6.70         6.69 -0.2%
7zip/7zip-benchmark                            14.84        14.80 -0.2%
tramp3d-v4/tramp3d-v4                           5.70         5.68 -0.3%
                           Geomean difference                     -0.2%
```

https://github.com/llvm/llvm-project/pull/90565