refactor(tvix/castore/blobservice/memory): use parking_lot RwLock

This one doesn't require us to deal with poisoning, is upgradeable and
the right thing to use when locking access to data, not IO resources.

Change-Id: I78634953a73404500d28f51f1d93a87e215c8149
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11612
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: Connor Brewster <cbrewster@hey.com>

tvix/Cargo.lock

@@ -2305,7 +2305,7 @@ dependencies = [
  "hyper 0.14.28",
  "itertools 0.12.0",
  "md-5",
- "parking_lot 0.12.1",
+ "parking_lot 0.12.2",
  "percent-encoding",
  "quick-xml",
  "rand",
@@ -2460,9 +2460,9 @@ dependencies = [
 
 [[package]]
 name = "parking_lot"
-version = "0.12.1"
+version = "0.12.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3742b2c103b9f06bc9fff0a37ff4912935851bee6d36f3c02bcc755bcfec228f"
+checksum = "7e4af0ca4f6caed20e900d564c242b8e5d4903fdacf31d3daf527b66fe6f42fb"
 dependencies = [
  "lock_api",
  "parking_lot_core 0.9.9",
@@ -4298,7 +4298,7 @@ dependencies = [
  "lazy_static",
  "libc",
  "object_store",
- "parking_lot 0.12.1",
+ "parking_lot 0.12.2",
  "petgraph",
  "pin-project-lite",
  "prost 0.12.3",
@@ -4472,6 +4472,7 @@ dependencies = [
  "opentelemetry",
  "opentelemetry-otlp",
  "opentelemetry_sdk",
+ "parking_lot 0.12.2",
  "pin-project-lite",
  "prost 0.12.3",
  "prost-build",