String equality in Case statement inside date transform function throws

Given a query as follows:
```
select
cast(
date_trunc(
'day',
datetime_convert(
datetime_convert(
date_timestamp + FromEpochDays(case when 'week' = 'week' then 1 else 0 end),
'1:MILLISECONDS:EPOCH',
'1:MILLISECONDS:SIMPLE_DATE_FORMAT:yyyy-MM-dd tz(UTC)',
'1:MILLISECONDS'
),.........
```
this throws with exception
```
ProcessingException(errorCode:150, message:SQLParsingError:
org.apache.pinot.sql.parsers.SqlCompilationException: Caught exception while invoking method: public static boolean org.apache.pinot.common.function.scalar.ComparisonFunctions.equals(double,double) with arguments: [week, week]
at org.apache.pinot.sql.parsers.rewriter.CompileTimeFunctionsInvoker.invokeCompileTimeFunctionExpression(CompileTimeFunctionsInvoker.java:87)
at org.apache.pinot.sql.parsers.rewriter.CompileTimeFunctionsInvoker.invokeCompileTimeFunctionExpression(CompileTimeFunctionsInvoker.java:65)
at org.apache.pinot.sql.parsers.rewriter.CompileTimeFunctionsInvoker.invokeCompileTimeFunctionExpression(CompileTimeFunctionsInvoker.java:65)
at org.apache.pinot.sql.parsers.rewriter.CompileTimeFunctionsInvoker.invokeCompileTimeFunctionExpression(CompileTimeFunctionsInvoker.java:65)
...
Caused by: java.lang.NumberFormatException: For input string: "week"
at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2054)
at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.base/java.lang.Double.parseDouble(Double.java:543)
at org.apache.pinot.common.utils.PinotDataType$11.toDouble(PinotDataType.java:621))
```

--
Previously this worked fine in an older version of Pinot, if you change the 'week' = 'week' to 2 = 2, it works, so something is wrong with the literal parsing. This is inside a case statement, so string comparison should be supported.

Start by reproducing the query through CompileTimeFunctionsInvoker.java, then inspect PinotDataType.java and the comparison path shown in the stack trace. Add a regression test for string equality inside a CASE expression and verify that the query no longer raises NumberFormatException while numeric comparisons continue to work.

Written by the indexing model from the issue text.