Improve instructions for last portion of walk leg

[binh-dam-ibigroup]

Checklist

• Appropriate branch selected (all PRs must first be merged to dev before they can be merged to master)
• Any modified or new methods or classes have helpful JavaDoc and code is thoroughly commented
• [na] The description lists all applicable issues this PR seeks to resolve
• [na] The description lists any configuration setting(s) that differ from the default settings
• All tests and CI builds passing

Description

This PR improves instructions on walk legs after the last turn is taken:

• "Continue" instructions, instead of "NO_INSTRUCTION", are given on the last street/sidewalk/path,
• If the destination is away from the last street/sidewalk/path in an itinerary, an instruction: "Your destination is in the vicinity" is emitted when the traveler reaches the end of the leg shape. (An extra step is added behind the scenes to accommodate that).

[br648]

All good.

[JymDyerIBI]

👍 These look good.