[Polymetis] Completely expose Franka Hand gripper API

[exhaustin]

Description

Issue #1398 highlights an inflexibility of franka::Gripper::move, which is currently the only API Polymetis is using to command the Franka Hand.
Basically the move command blocks until it reaches the desired goal, which causes problems during grasping.
This PR exposes franka::Gripper::grasp, which is a clunky API that at least allows the user to execute a grasp instead of commanding the gripper to 0 width.

Type of change

Please check the options that are relevant.

• Bug fix (non-breaking change that fixes an issue)
• Proposes a change (non-breaking change that isn't necessarily a bug)
• Refactor
• New feature (non-breaking change that adds a new functionality)
• Breaking change (fix or feature that would break some existing functionality downstream)
• This is a unit test
• Documentation only change
• Datasets Release
• Models Release

Type of requested review

• I want a thorough review of the implementation.
• I want a high level review.
• I want a deep design review.

Before and After

If this PR introduces a change or fixes a bug, please add before and after screenshots (if this is causes a UX change) or before and after examples(this could be plain text, videos etc ) to demonstrate the change.

If this PR introduces a new feature, please also add examples or screenshots demonstrating the feature.

Testing

Tested on hardware

Checklist:

• I have performed manual end-to-end testing of the feature in my environment.
• I have added Docstrings and comments to the code.
• I have made changes to existing documentation where needed.
• I have added tests that show that the PR is functional.
• New and existing unit tests pass locally with my changes.
• I have added relevant collaborators to review the PR before merge.
• [Polymetis only] I ran on hardware (1) all scripts in tests/scripts, (2) asv benchmarks.

[1heart]

Makes sense.

One question -- it looks like epsilon_inner/outer have different default values in Python/C++. Where are the values coming from?

[exhaustin]

Makes sense.

One question -- it looks like epsilon_inner/outer have different default values in Python/C++. Where are the values coming from?

That was from my original misunderstanding of how these parameters work. I thought they were upper and lower limits, and so I set the epsilon_inner to slightly below zero and epsilon_upper to larger than max width.
After learning that they were tolerances from the target grasp width, I just default them to large numbers.

[1heart]

Seems like mrp tests are broken here? Not sure why