[Module Proposal] `avm/res/scom/managed-instance`

### Check for previous/existing GitHub issues/module proposals

- [X] I have checked for previous/existing GitHub issues/module proposals.

### Check this module doesn't already exist in the module indexes

- [X] I have checked for that this module doesn't already exist in the module indexes; or I'm proposing the module to be migrated from CARML/TFVM.

### Bicep or Terraform?

Bicep

### Module Classification?

I'm not sure, please advise

### Module Name

avm/res/scom/managed-instance

### Module Details

This is a new Azure resource that has went public review on 12/12/2023. There is no Bicep module for it yet.

- Microsoft.Scom/managedInstances -- SCOM MI

### Do you want to be the owner of this module?

No

### Module Owner's GitHub Username (handle)

_No response_

### (Optional) Secondary Module Owner's GitHub Username (handle)

_No response_