feat: [Forge] set foreign key name manually

[stausif]

Description
Ref #5075

custom name for foreign key constraint can be added.

$this->forge->addForeignKey("column_name", "table_name", "id", "onDelete", "onUpdate", ["constraint"=>"foreignkey_name"])

auto create name for foreign key is still there, a check is added to choose between two.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[kenjis]

Thank you for the contribution!

But you sent this PR to the wrong branch.
The enhancement should be sent to 4.3 branch now.
See https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/pull_request.md#branching

Please fix it.
See #6329 (comment)

[kenjis]

If you sent to the wrong branch
https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/workflow.md#if-you-sent-to-the-wrong-branch

[stausif]

If you sent to the wrong branch https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/workflow.md#if-you-sent-to-the-wrong-branch

Thanks I'll update and resubmit it.

[kenjis]

#6468 was merged into 4.3.