pin-init upstream sync for v7.2 (round 1)

This series collects all upstream developments of pin-init to date and
synchronize them to the kernel tree.

A major change in this cycle is the bump of MSRV to 1.82 to get rid of
unstable features, following the kernel version bump in 7.1. The MSRV is
bumped straight to 1.85 as pin-init can also be used outside kernel, so we
avoid bumping unless there is a need for new version.

Here are the list of merged changes included in the series:

- examples: mark as `#[inline]` all `From::from()`s for `Error`
  Rust-for-Linux/pin-init#126
- bump minimum Rust version to 1.82
  Rust-for-Linux/pin-init#129
- cleanup `Zeroable` and `ZeroableOptions`
  Rust-for-Linux/pin-init#118
- internal: add missing where clause to projection types
  Rust-for-Linux/pin-init#121
- internal: internal: remove redundant `#[pin]` filtering
  Rust-for-Linux/pin-init#131

For information, here are the list of upstream-only changes, which are
related to Cargo or tests/CI changes only.

- build.rs: use `option_env!` to register env variable dependency
  Rust-for-Linux/pin-init#128
- clean up dependencies
  Rust-for-Linux/pin-init#130
- tests: add test for check correct macro hygiene 
  Rust-for-Linux/pin-init#133
- ci: use tagged release of actions
  Rust-for-Linux/pin-init#134
- ci: have a single job to gate all required jobs
  Rust-for-Linux/pin-init#138

Best,
Gary

--- b4-submit-tracking ---
# This section is used internally by b4 prep for tracking purposes.
{
  "series": {
    "revision": 1,
    "change-id": "20260414-pin-init-sync-ae407945a726",
    "prefixes": [],
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}

Author: nbdd0121