Use modular_bitfield to bitpack IndexEntry (#22447)

Cargo.lock

@@ -2625,6 +2625,27 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "modular-bitfield"
+version = "0.11.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a53d79ba8304ac1c4f9eb3b9d281f21f7be9d4626f72ce7df4ad8fbde4f38a74"
+dependencies = [
+ "modular-bitfield-impl",
+ "static_assertions",
+]
+
+[[package]]
+name = "modular-bitfield-impl"
+version = "0.11.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a7d5f7076603ebc68de2dc6a650ec331a062a13abaa346975be747bbfa4b789"
+dependencies = [
+ "proc-macro2 1.0.32",
+ "quote 1.0.10",
+ "syn 1.0.81",
+]
+
 [[package]]
 name = "multimap"
 version = "0.8.3"
@@ -4585,6 +4606,7 @@ dependencies = [
  "fs_extra",
  "log 0.4.14",
  "memmap2 0.5.2",
+ "modular-bitfield",
  "rand 0.7.3",
  "rayon",
  "solana-logger 1.10.0",