On fail support for statements other than regular-compound-stmt

[pcnfernando]

Description:
Relates to https://ballerina.io/spec/lang/master/#stmt-with-on-fail

With the current implementation, we have mistakenly added support for having on-fail for transaction and retry based on #337 (comment).

We anyway can wrap transaction within a do-onfail to achieve the same behavior.
I was wondering whether it makes sense to have this sugaring for error handling of transaction blocks specifically.

Suggested Labels:

Code sample that shows issue:

Related Issues:
Raised a lang issue as the current implementation has a spec deviation
ballerina-platform/ballerina-lang#37315.

[jclark]

At first sight, what the implementation is doing seems reasonable. Let me look at this in more detail.

[jclark]

Concretely issue is whether the grammar should have

retry-stmt
| transaction-stmt
| retry-transaction-stmt

in regular-compound-stmt rather than statement.

[jclark]

This also needs some wording changes. We need to consider retry X on fail Y as lexically enclosing retry X.