feat(contracts): Implement a default withdraw function

[satyajeetkolhapure]

What does this PR do?

This PR implements default behaviour of withdraw function at Abstract Portal level Default portal will also use the same behaviour for withdrawal function

Related ticket

Fixes #790

Type of change

• [ ] Chore
• [ ] Bug fix
• [x] New feature
• [ ] Documentation update

Check list

• [x] Unit tests for any smart contract change
• [ ] Contracts and functions are documented

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 74.11%. Comparing base (e56a25f) to head (3321d59).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #801 +/- ## =========================================== + Coverage 46.80% 74.11% +27.31% =========================================== Files 18 49 +31 Lines 391 908 +517 Branches 59 182 +123 =========================================== + Hits 183 673 +490 - Misses 205 232 +27 Partials 3 3 ```

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