### What changes were proposed in this pull request?
This PR proposes to make the `code` string interpolator treat escapes the same way as Scala's builtin `StringContext.s()` string interpolator. This will remove the need for an ugly workaround in `Like` expression's codegen.
### Why are the changes needed?
The `code()` string interpolator in Spark SQL's code generator should treat escapes like Scala's builtin `StringContext.s()` interpolator, i.e. it should treat escapes in the code parts, and should not treat escapes in the input arguments.
For example,
```scala
val arg = "This is an argument."
val str = s"This is string part 1. $arg This is string part 2."
val code = code"This is string part 1. $arg This is string part 2."
assert(code.toString == str)
```
We should expect the `code()` interpolator to produce the same result as the `StringContext.s()` interpolator, where only escapes in the string parts should be treated, while the args should be kept verbatim.
But in the current implementation, due to the eager folding of code parts and literal input args, the escape treatment is incorrectly done on both code parts and literal args.
That causes a problem when an arg contains escape sequences and wants to preserve that in the final produced code string. For example, in `Like` expression's codegen, there's an ugly workaround for this bug:
```scala
// We need double escape to avoid org.codehaus.commons.compiler.CompileException.
// '\\' will cause exception 'Single quote must be backslash-escaped in character literal'.
// '\"' will cause exception 'Line break in literal not allowed'.
val newEscapeChar = if (escapeChar == '\"' || escapeChar == '\\') {
s"""\\\\\\$escapeChar"""
} else {
escapeChar
}
```
### Does this PR introduce any user-facing change?
No.
### How was this patch tested?
Added a new unit test case in `CodeBlockSuite`.
Closes#27544 from rednaxelafx/fix-code-string-interpolator.
Authored-by: Kris Mok <kris.mok@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
b4769998ef