Allow passing distribution version name instead of version number (i.e., noble instead of 24.04)

[xtremekforever]

One thing I've noticed with using the generator is that you must provide the --distribution-version as the version number, and cannot use the code name as an alternative:

$ swift run swift-sdk-generator make-linux-sdk --distribution-version noble
[1/1] Planning build
Building for debugging...
[1/1] Write swift-version--149EBBC1E6AAC1E9.txt
Build of product 'swift-sdk-generator' complete! (13.26s)
Error: Linux distribution `ubuntu` with version `noble` is not supported by this generator.

However, Swift SDKs are output using the code names by default:

$ swift sdk list
6.1-RELEASE_ubuntu_jammy_aarch64
6.1.2-RELEASE_ubuntu_jammy_aarch64

This causes a problem for scripts, since now you need to have the distribution version number as well as the codename in the script:

DISTRO_NAME=ubuntu
DISTRO_VERSION=jammy
DISTRO_VERSION_GENERATOR=22.04

Although it is possible to pass the SDK name when running the generator, it seems like it would still be nicer to have this as an option to be able to pass the version code name to the generator.