[clangd] Force Dex to respect symbol collector flags
`Dex` should utilize `FuzzyFindRequest.RestrictForCodeCompletion` flags
and omit symbols not meant for code completion when asked for it.
The measurements below were conducted with setting
`FuzzyFindRequest.RestrictForCodeCompletion` to `true` (so that it's
more realistic). Sadly, the average latency goes down, I suspect that is
mostly because of the empty queries where the number of posting lists is
critical.
| Metrics | Before | After | Relative difference
| ----- | ----- | ----- | -----
| Cumulative query latency (7000 `FuzzyFindRequest`s over LLVM static index) |
6182735043 ns |
7202442053 ns | +16%
| Whole Index size | 81.24 MB | 81.79 MB | +0.6%
Out of 292252 symbols collected from LLVM codebase 136926 appear to be
restricted for code completion.
Reviewers: ioeric
Differential Revision: https://reviews.llvm.org/D52357
llvm-svn: 342866