Some std lib math functions throw Field does not exist error on runtime.

[angadgill92]

Build info:

Jsonnet commandline interpreter (Go implementation) v0.20.0
go version go1.23.3 darwin/arm64
OS: Mac OS Sequoia 15.0.1 (24A348)

Steps to reproduce:
Run:

$ jsonnet -e 'std.isInteger(12.1)'

Expected output:

false

Actual:

$ jsonnet -e 'std.isInteger(12.1)'
RUNTIME ERROR: Field does not exist: isInteger
	<cmdline>:1:1-14	$
	During evaluation

The output is similar for std.isDecimal, std.isEven and std.isOdd.