Add the `has` operator to conditional breakpoint

[zero-plusplus]

Support the detection of key names using regular expressions as follows.

; object := [ key: "value" }
/^k/ in object

[zero-plusplus]

The in operator searches for inheritance, so regular expression searches are not appropriate. Therefore, the extension will be suspended.

Instead, I will add a reduced-feature operator has that does not consider inherited properties.

The has operator is used in the following way Note that the order of specification is opposite to that of the in operator.

; obj := { key: "value" }
obj has "value"
obj not has "value"
obj has /^v/i
obj not has /^v/i