Removed limit param from vector_match()

[snej]

vector_match() no longer takes an optional 3rd parameter.
The limit should now be passed as the overall LIMIT of the SELECT.

Also switched to using MATCH instead of LIKE in the generated SQL, because I found MATCH is slightly more efficient.

Also, with the latest vectorsearch extension, there were a couple of test failures caused by unexpected "Untrained index..." warnings. Fixed them.

[pasin]

"N1QL Vector Search" test needs update.

[pasin]

Error from PR validation for "N1QL Vector Search" test failure:

[2024-06-24T20:23:12.728Z] -----------------------------------------------------------------------------------------------------------------------
[2024-06-24T20:23:12.728Z] N1QL Vector Search
[2024-06-24T20:23:12.728Z] -----------------------------------------------------------------------------------------------------------------------
[2024-06-24T20:23:12.728Z] /var/lib/jenkins/mobile/workspace/line_couchbase-lite-core_PR-2080/couchbase-lite-core/LiteCore/tests/N1QLParserTest.cc:573
[2024-06-24T20:23:12.728Z] .......................................................................................................................
[2024-06-24T20:23:12.728Z] 
[2024-06-24T20:23:12.728Z] /var/lib/jenkins/mobile/workspace/line_couchbase-lite-core_PR-2080/couchbase-lite-core/LiteCore/tests/N1QLParserTest.cc:580: FAILED:
[2024-06-24T20:23:12.728Z]   CHECK( translate("SELECT META().id, VECTOR_DISTANCE(vecIndex) AS distance " "WHERE VECTOR_MATCH(vecIndex, $target, 5) ORDER BY distance") == "{'ORDER_BY':[['.distance']],'WHAT':[['_.',['meta()'],'.id']," "['AS',['VECTOR_DISTANCE()','vecIndex'],'distance']]," "'WHERE':['VECTOR_MATCH()','vecIndex',['$target'],5]}" )
[2024-06-24T20:23:12.728Z] due to unexpected exception with messages:
[2024-06-24T20:23:12.728Z]   N1QL: SELECT META().id, VECTOR_DISTANCE(vecIndex) AS distance WHERE VECTOR_MATCH(vecIndex, $target, 5) ORDER BY
[2024-06-24T20:23:12.728Z]   distance
[2024-06-24T20:23:12.728Z]   {'ORDER_BY':[['.distance']],'WHAT':[['_.',['meta()'],'.id'],['AS',['VECTOR_DISTANCE()','vecIndex'],'distance']],
[2024-06-24T20:23:12.728Z]   'WHERE':['VECTOR_MATCH()','vecIndex',['$target'],5]}
[2024-06-24T20:23:12.728Z]   Too many arguments for function 'VECTOR_MATCH'

[cbl-bot]

Code Coverage Results:

Type	Percentage
branches	68.36
functions	79.29
instantiations	35.32
lines	78.91
regions	75.53