Report the actual self python version

[bluss]

Inspect the venv marker for the self python environment and report its version in rye --version output.

Example (installed with 3.11.7)

> RYE_HOME=xyz ./xyz/shims/rye --version
rye 0.28.0
commit: 0.27.0+8 (2111778b3 2024-02-28)
platform: linux (x86_64)
self-python: [email protected]
symlink support: true
uv enabled: true

> RYE_HOME=notinstalled ./xyz/shims/rye --version
rye 0.28.0
commit: 0.27.0+8 (2111778b3 2024-02-28)
platform: linux (x86_64)
self-python: not bootstrapped (target: [email protected])
symlink support: true
uv enabled: false