[UI Feature] Allow custom name in Create New Execution dialog

### Motivation: Why do you think this is important?

Flyte supports custom execution names from the CLI with `pyflyte run --remote --name my-run-name ...`. This is a pretty useful feature. Unfortunately, it seems impossible to do this when starting a workflow from the web UI.

### Goal: What should the final outcome look like, ideally?

Have an optional text field in the Create New Execution dialog which allows me to set a custom execution name.

### Propose: Link/Inline OR Additional context

_No response_

### Are you sure this issue hasn't been raised already?

- [x] Yes

### Have you read the Code of Conduct?

- [x] Yes

Start at the web UI's Create New Execution dialog and compare its submission path with the CLI entry point `pyflyte run --remote --name`. Add an optional execution-name field whose value reaches the workflow launch, and verify that leaving it blank preserves the existing behavior. Done when a UI-launched workflow uses the entered custom name.

Written by the indexing model from the issue text.