[SQL] Remove BeamSql Prefix from class names

It feels redundant to have almost all files in sdks/java/extensions/sql to start with BeamSql:

```

kedin@kedin-macbookpro ~/w/beam> find . -name "BeamSql*.java" | grep -o "BeamSql.*"
BeamSqlParserImplTokenManager.java
BeamSqlParserImplConstants.java
BeamSqlParserImpl.java
BeamSqlParserImplTokenManager.java
BeamSqlParserImplConstants.java
BeamSqlParserImpl.java
BeamSqlFnExecutorTestBase.java
BeamSqlFnExecutorTest.java
BeamSqlCastExpressionTest.java
BeamSqlAndOrExpressionTest.java
BeamSqlCurrentTimestampExpressionTest.java
BeamSqlDateFloorExpressionTest.java
BeamSqlCurrentDateExpressionTest.java
BeamSqlCurrentTimeExpressionTest.java
BeamSqlDateCeilExpressionTest.java
BeamSqlIntervalMultiplyExpressionTest.java
BeamSqlTimestampMinusIntervalExpressionTest.java
BeamSqlDateExpressionTestBase.java
BeamSqlExtractExpressionTest.java
BeamSqlDatetimeMinusExpressionTest.java
BeamSqlDatetimePlusExpressionTest.java
BeamSqlTimestampMinusTimestampExpressionTest.java
BeamSqlCompareExpressionTest.java
BeamSqlPrimitiveTest.java
BeamSqlInputRefExpressionTest.java
BeamSqlCaseExpressionTest.java
BeamSqlMathBinaryExpressionTest.java
BeamSqlMathUnaryExpressionTest.java
BeamSqlReinterpretExpressionTest.java
BeamSqlNotExpressionTest.java
BeamSqlUdfExpressionTest.java
BeamSqlArithmeticExpressionTest.java
BeamSqlUpperExpressionTest.java
BeamSqlInitCapExpressionTest.java
BeamSqlCharLengthExpressionTest.java
BeamSqlLowerExpressionTest.java
BeamSqlTrimExpressionTest.java
BeamSqlOverlayExpressionTest.java
BeamSqlSubstringExpressionTest.java
BeamSqlConcatExpressionTest.java
BeamSqlPositionExpressionTest.java
BeamSqlStringUnaryExpressionTest.java
BeamSqlParserTest.java
BeamSqlRowCoderTest.java
BeamSqlDslJoinTest.java
BeamSqlDslFilterTest.java
BeamSqlDslProjectTest.java
BeamSqlApiSurfaceTest.java
BeamSqlNonAsciiTest.java
BeamSqlCliTest.java
BeamSqlDslBase.java
BeamSqlStringFunctionsIntegrationTest.java
BeamSqlMathFunctionsIntegrationTest.java
BeamSqlBuiltinFunctionsIntegrationTestBase.java
BeamSqlComparisonOperatorsIntegrationTest.java
BeamSqlArithmeticOperatorsIntegrationTest.java
BeamSqlLogicalFunctionsIntegrationTest.java
BeamSqlDateFunctionsIntegrationTest.java
BeamSqlConditionalFunctionsIntegrationTest.java
BeamSqlDslAggregationTest.java
BeamSqlDslUdfUdafTest.java
BeamSqlFnExecutor.java
BeamSqlExpressionExecutor.java
BeamSqlInputRefExpression.java
BeamSqlCaseExpression.java
BeamSqlReinterpretExpression.java
BeamSqlIntervalMultiplyExpression.java
BeamSqlExtractExpression.java
BeamSqlCurrentTimeExpression.java
BeamSqlTimestampMinusTimestampExpression.java
BeamSqlCurrentDateExpression.java
BeamSqlTimestampMinusIntervalExpression.java
BeamSqlDateCeilExpression.java
BeamSqlCurrentTimestampExpression.java
BeamSqlDateFloorExpression.java
BeamSqlDatetimePlusExpression.java
BeamSqlDatetimeMinusExpression.java
BeamSqlWindowExpression.java
BeamSqlWindowEndExpression.java
BeamSqlRoundExpression.java
BeamSqlPiExpression.java
BeamSqlMathUnaryExpression.java
BeamSqlAcosExpression.java
BeamSqlTanExpression.java
BeamSqlRandIntegerExpression.java
BeamSqlCeilExpression.java
BeamSqlAtan2Expression.java
BeamSqlAbsExpression.java
BeamSqlSignExpression.java
BeamSqlMathBinaryExpression.java
BeamSqlPowerExpression.java
BeamSqlExpExpression.java
BeamSqlLnExpression.java
BeamSqlCotExpression.java
BeamSqlCosExpression.java
BeamSqlAtanExpression.java
BeamSqlRandExpression.java
BeamSqlLogExpression.java
BeamSqlAsinExpression.java
BeamSqlDegreesExpression.java
BeamSqlTruncateExpression.java
BeamSqlSinExpression.java
BeamSqlFloorExpression.java
BeamSqlRadiansExpression.java
BeamSqlCastExpression.java
BeamSqlUdfExpression.java
BeamSqlOrExpression.java
BeamSqlAndExpression.java
BeamSqlLogicalExpression.java
BeamSqlNotExpression.java
BeamSqlPlusExpression.java
BeamSqlModExpression.java
BeamSqlDivideExpression.java
BeamSqlMinusExpression.java
BeamSqlArithmeticExpression.java
BeamSqlMultiplyExpression.java
BeamSqlEqualsExpression.java
BeamSqlGreaterThanExpression.java
BeamSqlIsNullExpression.java
BeamSqlLessThanExpression.java
BeamSqlIsNotNullExpression.java
BeamSqlNotEqualsExpression.java
BeamSqlCompareExpression.java
BeamSqlGreaterThanOrEqualsExpression.java
BeamSqlLessThanOrEqualsExpression.java
BeamSqlInitCapExpression.java
BeamSqlTrimExpression.java
...

```

Imported from Jira [BEAM-3463](https://issues.apache.org/jira/browse/BEAM-3463). Original Jira may contain additional context.
Reported by: kedin.

Start in sdks/java/extensions/sql by running the find command shown in the issue and reviewing the BeamSql-prefixed classes and tests it lists, including BeamSqlParserImpl.java and BeamSqlCliTest.java. Map the affected references before changing names; done means the redundant BeamSql prefix is removed consistently without broken references or tests.

Written by the indexing model from the issue text.