Revert "[lib][trace] std::sync -> fuchsia_sync"

This reverts commit b10a9470dd9e174f98c950e76943f80586cbd407.

Reason for revert: Potential culprit for core.vim3-vg-hwasan  failures

Original change's description:
> [lib][trace] std::sync -> fuchsia_sync
>
> The behaviors of fuchsia_sync's locks are very similar to those from
> the standard library. std::sync::Mutex is a port of the libsync
> mutex that fuchsia_sync::Mutex links against, and fuchsia_sync::RwLock
> is very similar to the std::sync::RwLock's futex-based approach. However
> there are some important differences:
>
> 1. fuchsia_sync supports lock cycle detection which surfaces many
>     deadlocks. See the documentation[0] for more details.
> 2. fuchsia_sync doesn't support lock poisoning because most of
>    Fuchsia's code is compiled with panic=abort.
>     a. saves memory with smaller types
>     b. avoids noop error handling syntax and branches
>
> [0]: https://fuchsia.dev/fuchsia-src/development/debugging/lock_cycles
>
> Bug: 465178981
> Cq-Include-Trybots: luci.fuchsia.try:core.arm64-debug,core.x64-debug;luci.turquoise.global.try:core.arm64-vg-debug,core.x64-vg-debug
> Change-Id: I5510a126bac91f68126b9c23ccb606e0337a3d3b
> Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1440147
> Reviewed-by: Gwen Mittertreiner <[email protected]>
> Fuchsia-Auto-Submit: Adam Perry <[email protected]>
> Commit-Queue: Adam Perry <[email protected]>

Bug: 465178981
Cq-Include-Trybots: luci.fuchsia.try:core.arm64-debug,core.x64-debug;luci.turquoise.global.try:core.arm64-vg-debug,core.x64-vg-debug
Change-Id: Ie9d65183ba4ebdccd7e62bfb4d254abfe5e8b011
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1443308
Commit-Queue: Sarah Chan <[email protected]>
Reviewed-by: RubberStamper 🤖 <[email protected]>

• src/lib/trace/rust/BUILD.gn[diff]
• src/lib/trace/rust/test/lib.rs[diff]