Rationaizing Resource Specification errors acorss executors.

[Harichandra-Prasath]

Description

There are three places where the executors raise the errors regarding resource specification.

1. when passing the resource_specification parameter to the htex, it raises the mpi_prefix_composer InvalidResourceSpecification from validate_resource_spec method. https://github.com/Parsl/parsl/blob/master/parsl/executors/high_throughput/executor.py#L342

2. ThreadPoolExecutor also raises the UnsupportedFeatureError when passing resource specification to it, https://github.com/Parsl/parsl/blob/master/parsl/executors/threads.py#L54

3. WorkQueueExecutor raises two errors similar to this but as a Base ExecutorError, one when there is invalid resource_specification ; https://github.com/Parsl/parsl/blob/master/parsl/executors/workqueue/executor.py#L418 and another one when the autolabel is false and resource_specification is not right, https://github.com/Parsl/parsl/blob/master/parsl/executors/workqueue/executor.py#L429

This PR rationalize these errors by creating a InvalidResourceSpecificationError in executors.error and using it across the executors. Moreover InvalidResourceSpecification and MissingResourceSpecification is removed from mpi_prefix_composer and places where the above two used were replaced with InvalidResourceSpecificationError.

Changed Behaviour

From this PR, All executors will raise InvalidResourceSpecificationError for errors regarding resource_spec.

Fixes

Fixes #3589

Type of change

• Bug fix
• Code maintenance/cleanup