[clangd] New CC Ranking Model to fix bad inference due to overflow.

[usaxena95]

Summary

Unreachable file distances are represented as std::numeric_limits<unsigned>::max().
The previous dataset recorded the signals as signed int capturing this default value
as -1.

A new dataset was regenerated and a new model is trained that interprets this
unreachable as the intended value.

Distribution of SymbolScopeDistance:

Value         Frequency(%)
0             46.6184
4294967295    29.5342
6             14.5666
4              6.4433
2              1.4534
8              0.5760
10             0.3581
....

Distribution of FileProximityDistance:

Value         Frequency(%)
4294967295    39.9378
12             5.1997
14             4.9828
15             4.4221
16             4.3820
13             4.2765
17             3.8957
11             3.6387
19             3.4799
18             3.4076
....

[usaxena95]

Update model to LambdaMART instead of XE_NDCG.