Introduce an exception type for the AST Json importer and use as replacements for `solAsserts`

[matheusaaguiar]

Suggested here: #15463 (comment)

The AST Json Importer has many instances of solAssert being used for validation/error messaging. As suggested in the linked comment, it would be better to have a specific exception for those cases.
Also, note that currently exceptions are not caught in standard JSON mode and that needs to be adjusted as well.

[krishnabandewar]

i would like to hndle this ?