Remove 'same member name' restriction for parmlib members

[arthurcoucker]

Describe the solution you'd like
It is a significant improvement that parmlib members can now be used for the configuration files. However there is a restriction that the members need to have the same name. That implies that two configuration files cannot be saved in the same PDS.

Describe alternatives you've considered
If for example one uses AHLQ.PARMLIB(ZWEYAML) for the base config and AHLQ.PARMLIB(UMSYML) for the IZP configuration, this is not possible. We could bypass the problem by copying (e.g. DFSORT) the UMS member with rename to a temporary PDS in a step before the STC proc starting.
CONFIG=PARMLIB(AHLQ.PARMLIB(ZWEYAML))\
:PARMLIB(AHLQ.TMP.PARMLIB(ZWEYAML))

But these are creative solutions that could be left away if the restriction is gone.

Additional context
"Zowe can now start using zowe.yaml loaded from PARMLIB members if you want, when using the STC startup as well as the zwe start, zwe stop, and zwe components commands. These can be specified in --config / CONFIG input as PARMLIB() entries. For example, zwe start --config FILE(/my/customizations.yaml):PARMLIB(TEAM.CUSTOM.ZOWE(YAML)):PARMLIB(ORG.CUSTOM.ZOWE(YAML)):FILE(/zowe/defaults.yaml) ... Note when using PARMLIB, every member name must be the same."

This requirement is not absolutely necessary, but it would remove an inconvenient restriction and make working with the parmlib datasets easier.

[JoeNemo]

Ok, we understand the requirement, but probably worry about a breaking change for Zowe products that make the assumption that the config member names are all the same. But we need to re-investigate when moving to V4.