perf: rewrite field:* to _exists_:field

[dkharms]

Description

We can rewrite queries like trace_id:* to _exists_:trace_id in regular search requests. The latter query is significantly lighter and significantly easier to compute because we have special _exists_ index type.

This way we do not need to build huge tree of iterators over all possible token values.

Back-of-the-envelope benchmarks:

| 0 | | # |   query    | type |            metrics            | |
|   | |---|------------|------|-------------------------------| |
|   | | 0 | trace_id:* | cold | | # |    name     |  value  | | |
|   | |   |            |      | |---|-------------|---------| | |
|   | |   |            |      | | 0 | mean (ms)   |   83.18 | | |
|   | |   |            |      | | 1 | stddev (ms) |   11.33 | | |
|   | |   |            |      | | 2 | p(50) (ms)  |   79.30 | | |
|   | |   |            |      | | 3 | p(95) (ms)  |   96.79 | | |
|   | |   |            |      | | 4 | p(99) (ms)  |  102.81 | | |
|   | |   |            |      | | 5 | iterations  |      24 | | |
|   | |   |            |      | | 6 | total       | 1019553 | | |
| 1 | | # |   query    | type |            metrics            | |
|   | |---|------------|------|-------------------------------| |
|   | | 0 | trace_id:* | cold | | # |    name     |  value  | | |
|   | |   |            |      | |---|-------------|---------| | |
|   | |   |            |      | | 0 | mean (ms)   |  340.77 | | |
|   | |   |            |      | | 1 | stddev (ms) |    9.94 | | |
|   | |   |            |      | | 2 | p(50) (ms)  |  336.56 | | |
|   | |   |            |      | | 3 | p(95) (ms)  |  357.86 | | |
|   | |   |            |      | | 4 | p(99) (ms)  |  381.04 | | |
|   | |   |            |      | | 5 | iterations  |      21 | | |
|   | |   |            |      | | 6 | total       | 1019725 | | |

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🔴 Performance Degradation

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Name	Previous	Current	Ratio	Verdict
MutexListAppend-4	a73114	4a34dc
	194.53 MB/s	174.79 MB/s	0.90	🔴