[gdcm]Update to v3.0.0 and rename to gdcm.

[JackBoosY]

• Update to v3.0.0
• Rename this port name to gdcm because its version is no longer 2.x.x.
• Fix dependencies.
• Fix share path.
• Add empty port gdcm2 mapping to gdcm.

Relate: #6338.

[JackBoosY]

All the triplets are passed. CI failed because its name has changed.

[Rastaban]

I'm concered about breaking someone because we changed the name of the port, but I agree that gdcm is a better name. Could you bring back the gdcm2 port with a CONTROL file

Source: gdcm2
Version: deprecated
Description: This port was renamed to gdcm.  The gdcm2 name is deprecated.
Build-Depends: gdcm

portfile.cmake can just contain set(VCPKG_POLICY_EMPTY_PACKAGE enabled) along with a message about the port being renamed.

[JackBoosY]

@Rastaban yeah, I agree with you. I added empty port gdcm2 mapping to gdcm.