feat(PhyslibAlpha): add line surface

[Robby955]

Summary

• add the coordinate line surface API in PhyslibAlpha.SpaceAndTime.Space.Surfaces.Line
• define the pushed-forward line measure, its temperate-growth instance, and the associated distribution
• prove the embedded line has ambient volume zero

[github-actions]

Thank you for this PR, which will now be reviewed.
If submitting to ./Physlib or ./QuantumInfo, please
see our review guidelines
if you are not familiar with the process. You should expect a back and forth
with a reviewer before your PR is merged. See also that link for how to
add appropriate labels to your PR. The PR will also go through a number
of automated checks. You can learn more about these here,
including how to run them locally.

If you are submitting to ./PhyslibAlpha there will be a lighter review process,
though your PR must still pass the automated checks.

If you want to bring attention to this PR, please write a message on this
thread of the Lean Zulip.

[jstoobysmith]

Great! Looks good to me! Approved, and will merge shortly.

[jstoobysmith]

Many thanks for your first PR :)