allow runtime configurable log buffer size, drop circular_buffer crate dep

Cargo.lock

@@ -201,12 +201,6 @@ dependencies = [
  "windows-link",
 ]
 
-[[package]]
-name = "circular-buffer"
-version = "1.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "14c638459986b83c2b885179bd4ea6a2cbb05697b001501a56adb3a3d230803b"
-
 [[package]]
 name = "clap"
 version = "4.5.53"
@@ -1682,7 +1676,6 @@ name = "signal-gateway"
 version = "0.1.0"
 dependencies = [
  "chrono",
- "circular-buffer",
  "conf",
  "conf-extra",
  "displaydoc",