Add support for ESAM avail settings in AWS::MediaLive::Channel

### Name of the resource

AWS::MediaLive::Channel

### Resource name

_No response_

### Description

AWS MediaLive has new feature that is not supported in CloudFormation. In AWS::MediaLive::Channel > EncoderSettings > AvailConfiguration > AvailSettings, only Scte35SpliceInsert and Scte35TimeSignalApos are supported now. MediaLive now has a 3rd option, ESAM, that should be added.

Ref. https://awscli.amazonaws.com/v2/documentation/api/latest/reference/medialive/create-channel.html?highlight=esam

Enabling ESAM under AvailSettings would be:
"Esam": {
"AcquisitionPointId": "string",
"AdAvailOffset": integer,
"PasswordParam": "string",
"PoisEndpoint": "string",
"Username": "string",
"ZoneIdentity": "string"
}

### Other Details

_No response_

Start at AWS::MediaLive::Channel > EncoderSettings > AvailConfiguration > AvailSettings and compare the existing Scte35SpliceInsert and Scte35TimeSignalApos support with the AWS MediaLive create-channel reference. Add the ESAM settings fields listed in the issue, then verify that the resource accepts and represents an Esam configuration.

Written by the indexing model from the issue text.