As a developer I want to configure the task definition suffix

## Problem

Currently to enable task definition IntelliSense we need to suffix the task definition files with "ecs-task-def.json". This is not possible in all development environments. We have specific pipelines and processes in place that expect task definitions files to have a specific name. Hence we cannot use the task definition IntelliSense

## Expected behavior

Allow developers to configure in vscode the suffix or naming scheme needed to activate the task definition IntelliSense.

examples:
`"aws.ecs.taskDefinitionPattern": "*-def.json"`
`"aws.ecs.taskDefinitionPattern": "FixedName.json"`

or support many:
`"aws.ecs.taskDefinitionPatterns": ["*-def.json", "FixedName.json"]`

The issue names no files or tests. Start by locating the ECS task-definition IntelliSense activation logic and the existing VS Code configuration declarations, then trace how the current ecs-task-def.json suffix is recognized. Done means configured single or multiple patterns activate IntelliSense while preserving existing behavior.

Written by the indexing model from the issue text.