evalengine: Support built-in MySQL function Abs

[tianshishuo]

Description

evalengine: Support built-in MySQL function Abs

Related Issue(s)

evalengine: Support all built-in MySQL functions

Checklist

• [ ] Should this PR be backported?
• [ ] Tests were added or are not required
• [ ] Documentation was added or is not required

Deployment Notes

[frouioui]

Hello @tianshishuo and thank you for your first contribution 🎉 Please make sure you've read https://github.com/vitessio/vitess/issues/9647#issuecomment-1054423282 if you didn't already.

[github-actions[bot]]

This PR is being marked as stale because it has been open for 30 days with no activity. To rectify, you may do any of the following:

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If no action is taken within 7 days, this PR will be closed.

[github-actions[bot]]

This PR was closed because it has been stale for 7 days with no activity.