Enable specification of target hostname for a dragon task

[ankona]

Description

This PR adds two features:

1. Ability to specify hostnames that tasks should run on
2. Enable tasks colocation

Specifying Hostnames

The existing DragonRunRequest supported the ability to specify a hostname when creating a policy used to run a task. However, the hostnames were not exposed to clients.

This ticket allows clients to pass a list of hosts that will be used in place of the default "first available host" behavior.

Task Colocation

The prior system for finding nodes to execute a task worked worked only with unassigned nodes. Any node assigned a task could not be assigned another task.

This ticket adds a more capable prioritizer class that enables clients using hostnames to colocate tasks. It also retains the capability to return open nodes when no hostname is specified.

[codecov]

Codecov Report

Attention: Patch coverage is 65.60284% with 97 lines in your changes missing coverage. Please review.

Please upload report for BASE (mli-feature@f7ef49b). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
smartsim/_core/launcher/dragon/dragonBackend.py	0.00%	78 Missing ⚠️
smartsim/_core/launcher/dragon/pqueue.py	90.10%	19 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##             mli-feature     #660   +/-   ##
==============================================
  Coverage               ?   79.26%           
==============================================
  Files                  ?       98           
  Lines                  ?     7914           
  Branches               ?        0           
==============================================
  Hits                   ?     6273           
  Misses                 ?     1641           
  Partials               ?        0           

Files with missing lines	Coverage Δ
smartsim/_core/launcher/dragon/dragonLauncher.py	50.00% <100.00%> (ø)
smartsim/_core/launcher/step/dragonStep.py	94.59% <100.00%> (ø)
smartsim/settings/dragonRunSettings.py	94.44% <100.00%> (ø)
smartsim/_core/launcher/dragon/pqueue.py	90.10% <90.10%> (ø)
smartsim/_core/launcher/dragon/dragonBackend.py	1.96% <0.00%> (ø)

---- 🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[mellis13]

Just some initial comments while you are making updates. Love the robust commenting and documentation! It really helped make the review process easier and makes the code more maintainable.

[AlyssaCote]

You resolved all of my previous comments with your new updates! This looks great me, just a few clean up comments.

[mellis13]

Thanks for all of the updates. Just a couple of comments but overall love the improvements!

[al-rigazzi]

LGTM, this looks awesome! The Backend is slowly but steadily getting much more readable, thanks!