devel/py-installer: convert to PEP-517 build and packaging

[vishwin]

Summary

Per description. Pretty much everything following PEP-517 will use this tool during stage so important to remove all dependencies to prevent loops, especially when this gets incorporated into the framework. Recommended to try this after D34786 but can work as-is.

Not compiling bytecode, not only because RECORD does not include them, but also as a long-term goal to compile them on install rather than stage time (D34739)

Test Plan

Like D34786, not currently seeking approval to commit. Successfully packages, passes QA and installs consumers as intended.

[vishwin]

update to 0.6.0 and use framework

[vishwin]

rebase

[vishwin]

MAINTAINER to python@ as infrastructure

[fluffy]

Good step.

[vishwin]

convert to DISTVERSION, bump PORTREVISION, fix PEP517_BUILD_DEPEND

[vishwin]

another round of stray paths smh