[clang] [clang][analyzer] Enable loop unrolling by default (PR #178911)

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gamesh411 wrote:

My time measurements on some OS projects:
| Project | Baseline (seconds) | Loop Unroll (seconds) | Time Absolute Change (seconds) | % Change | Reports Num Change |
|---------|-------------------:|----------------------:|-------------------------------:|---------:|-------------------:|
| codechecker | 6 | 6 | +0 | +0.0% | +0 |
| memcached | 27 | 28 | +1 | +3.7% | +0 |
| tmux | 78 | 80 | +2 | +2.6% | +0 |
| curl | 123 | 125 | +2 | +1.6% | +0 |
| twin | 49 | 49 | +0 | +0.0% | +0 |
| vim | 165 | 173 | +8 | +4.8% | -36 |
| openssl | 255 | 269 | +14 | +5.5% | +0 |
| sqlite | 919 | 940 | +21 | +2.3% | +2 |
| ffmpeg | 1278 | 1304 | +26 | +2.0% | +6 |
| postgres | 330 | 344 | +14 | +4.2% | +3 |
| tinyxml2 | 31 | 31 | +0 | +0.0% | +0 |
| libwebm | 64 | 62 | -2 | -3.1% | +0 |
| xerces | 184 | 189 | +5 | +2.7% | +1 |
| bitcoin | 175 | 190 | +15 | +8.6% | +0 |
| protobuf | 2073 | 2175 | +102 | +4.9% | +3 |
| qtbase | 2832 | 2952 | +120 | +4.2% | +3 |
| contour | 581 | 604 | +23 | +4.0% | +0 |
| TOTAL | 9170 | 9521 | +351 | +3.8% | -18 |

### Overall Performance Impact
Measured: +3.83% overhead
95% Confidence Interval: [+3.82%, +3.84%]

https://github.com/llvm/llvm-project/pull/178911