fix(snuba-search): Fix how we calculate hits

[snigdhas]

From https://github.com/getsentry/sentry/pull/68374#discussion_r1559835949, we need to add the sampled calculations when counting the number of hits for queries that required a post-filter for Postgres fields.

This PR replicates the logic used in the PostgresSnubaQueryExecutor. I've tested locally to verify the counts work as expected.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

:white_check_mark: All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/sentry/search/snuba/executors.py	87.50%	0 Missing and 1 partial :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #78545   +/-   ##
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  Coverage   78.11%   78.11%           
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  Files        7082     7082           
  Lines      312250   312259    +9     
  Branches    51010    51011    +1     
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+ Hits       243910   243923   +13     
+ Misses      61984    61981    -3     
+ Partials     6356     6355    -1