Add feature to send OTPs in e-mail verifications.

[shanggeeth]

This is implemented as fix to the wso2/product-is#14808
Applying changes from #617

Following are the changes introducing through this PR.

1. Checkbox (Send OTP in E-mail) to configure whether to send a confirmation code or a OTP in verification/confirmation e-mail.
2. Three checkboxes (Use uppercase characters in OTP, Use lowercase characters in OTP, User numbers in OTP) to define OTP pattern for e-mail and SMS OTPs.
3. Input field to include the length for the OTPs.

These changes are introduced to the below flows.

1. Self Registration
2. Lite Registration
3. Ask Password
4. User Claim Update.
5. Notification based Password Recovery

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}