[Bug]: Computed name field did not give run-time error for immutable type

[prakanth97]

Description

import ballerina/io;

const x = "a";
readonly X = {a : "A", [x] : "B"};

public function main() {
    io:println(X);
}

Currently it returns {"a":"B"}. But spec says,

A mapping-constructor-expr first constructs a mapping value without considering any computed-name-field. 
The effect of a computed-name-field is to modify the member of the mapping with the specified name after 
the mapping has been constructed. If the modification is incompatible with the inherent type, then the 
mapping-constructor-expr will panic. The modifications are performed in the order in which the computed-name-fields
 occur in the mapping-constructor-expr.

The modification should be panic for immutable types.

Steps to Reproduce

No response

Affected Version(s)

2201.5.0
Master

OS, DB, other environment details and versions

No response

Related area

-> Compilation

Related issue(s) (optional)

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Suggested label(s) (optional)

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Suggested assignee(s) (optional)

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[MaryamZi]

While the const scenario will be disallowed once ballerina-platform/ballerina-spec#772 is addressed, this also disallows the non-const case which is kinda too restrictive IMO.

Related to ballerina-platform/ballerina-spec#532.
Created ballerina-platform/ballerina-spec#1245.