fix(build): support non-Linux Unix targets (illumos/Solaris/*BSD) (#5853)

* fix(build): support non-Linux Unix targets (illumos/Solaris/*BSD)

Two independent build-infrastructure blockers kept RustFS from building on
non-Linux Unix platforms. Neither touches runtime logic.

1. pulsar regenerates its protobuf bindings in build.rs on every build, which
   needs `protoc`. Platforms without a packaged protoc (illumos/Solaris/*BSD)
   now enable pulsar's `protobuf-src` feature via a cfg-gated dependency, which
   builds a vendored protoc from C++ sources. Mainstream targets keep the lean
   dependency and their existing system/CI protoc.

2. clocksource 0.8.3 (pulled in transitively by ratelimit 0.10) used the
   Linux-only `CLOCK_MONOTONIC_COARSE`. ratelimit 2.0 dropped the clocksource
   dependency entirely, so upgrading removes the portability problem at the
   root rather than patching clocksource. The bandwidth throttle's bulk
   `consume()` is rewritten onto ratelimit 2.0's `try_wait_n`, preserving the
   best-effort partial-consumption semantics.

Verified: cargo check + bandwidth monitor unit tests pass; cargo tree confirms
protobuf-src is enabled only for illumos/Solaris/*BSD and clocksource is gone
from the graph. The final illumos build must be confirmed on-platform.

Closes #3195

* fix(ecstore): guard ratelimit v2 capacity overflow

Co-Authored-By: heihutu <heihutu@gmail.com>

* test(ecstore): avoid slow bandwidth reader timeout

Co-Authored-By: heihutu <heihutu@gmail.com>

* fix(targets): drop vendored pulsar protobuf build

Co-Authored-By: heihutu <heihutu@gmail.com>

---------
Co-authored-by: houseme <housemecn@gmail.com>
Co-authored-by: heihutu <heihutu@gmail.com>

Cargo.lock

@@ -2006,17 +2006,6 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c8d4a3bb8b1e0c1050499d1815f5ab16d04f0959b233085fb31653fbfc9d98f9"
 
-[[package]]
-name = "clocksource"
-version = "0.8.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "46a4f8c23584e9dc6e40de1406e8c776ae727c49f7cb85c0bb23fb8c2096f7e0"
-dependencies = [
- "libc",
- "time",
- "winapi",
-]
-
 [[package]]
 name = "cmake"
 version = "0.1.58"
@@ -8394,12 +8383,10 @@ dependencies = [
 
 [[package]]
 name = "ratelimit"
-version = "0.10.1"
+version = "2.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5dc94ed8e3de45f6d8d052869d48c0dbeebcaa7a6c345ec7f0f917e10347428e"
+checksum = "e78b08065c51c82ff8c4a0d88e3dce3edfce39c375e946c3464210fff3433fb8"
 dependencies = [
- "clocksource",
- "parking_lot",
  "thiserror 2.0.20",
 ]