perf: improve wildcard query perf with predicate and contains-check pushdown

[cheb0]

Description

Currently we spend only a fraction of time calling bytes.Index. This PR partially addresses that.

This PR pushes pattern.Searcher to Block level, so that Block is able to stream tokens through searcher. For ordinary wildcards like *error* there is direct FindContains method which is even faster.

For example, query message:*foobarf*:
main: 86 ms
using FindToken: 50 ms
using FindContains: 37 ms

So, FindContains just throws out costly abstractions to get additional performance. We could also provide a dedicated func like FindSuffix, for example. This is a typical example when performance requires additional code.

Query	Type	Ids	cold, ms	hot, ms	cold (branch), ms	hot (branch), ms	cold diff	hot diff
trace_id:*foobar	reg	0	18.76	4.37	16.14	1.84	-14%	-57.9%
k8s_pod:*6	reg	100	13.3	0.67	13.03	0.47	-2%	-29.9%
message:*err*	reg	100	138.72	26.97	120.27	12.36	-13.3%	-54.2%
message:*foo*	reg	100	77.69	27.08	60.54	11.84	-22.1%	-56.3%
message:*request*	reg	100	124.95	25.45	104.13	10.37	-16.7%	-59.3%
message:*foobar*foobar*	reg	0	187.54	64.25	147.31	30.5	-21.5%	-52.5%
message:*foobarfoobar*	reg	0	184.93	63.87	121.51	20.39	-34.3%	-68.1%
message:*very_very_message_aggregator_events*	reg	0	173.45	51.62	116.9	12.81	-32.6%	-75.2%

Next steps:

• try calling bytes.Index over Block payload - already shows good results
• build Offsets lazy - if previous is done
• modernize token Block, boost Unpack speed

---

• I have read and followed all requirements in CONTRIBUTING.md;
• I used LLM/AI assistance to make this pull request;

[codecov-commenter]

Codecov Report

❌ Patch coverage is 88.50575% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.70%. Comparing base (0a1f2c1) to head (c61bdab).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
frac/active_token_list.go	78.94%	2 Missing and 2 partials ⚠️
frac/sealed/token/block_loader.go	86.66%	1 Missing and 1 partial ⚠️
frac/sealed/token/provider.go	90.00%	1 Missing and 1 partial ⚠️
pattern/pattern.go	91.30%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #397      +/-   ##
==========================================
+ Coverage   70.58%   70.70%   +0.12%     
==========================================
  Files         222      222              
  Lines       17375    17441      +66     
==========================================
+ Hits        12264    12332      +68     
+ Misses       4195     4191       -4     
- Partials      916      918       +2     

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