Fix available_memory

[yito88]

Describe your changes

The available_memory unit was changed from KB to Byte when sysinfo was updated from v0.21.1 to v0.29.4 at #1695.

v0.21.1: https://docs.rs/sysinfo/0.21.1/sysinfo/trait.SystemExt.html#tymethod.available_memory

Returns the amount of available RAM in KB.

v0.29.4: https://docs.rs/sysinfo/0.29.4/sysinfo/trait.SystemExt.html#tymethod.available_memory

Returns the amount of available RAM in bytes.

The WASM cache size and the RocksDB cache size were huge due to this issue.

2023-08-09T19:07:13.014083Z  INFO namada_apps::node::ledger: VP WASM compilation cache size not configured, using 1/6 of available memory.
2023-08-09T19:07:13.014154Z  INFO namada_apps::node::ledger: Available memory: 29.93 TiB
2023-08-09T19:07:13.014163Z  INFO namada_apps::node::ledger: VP WASM compilation cache size: 4.99 TiB
2023-08-09T19:07:13.014169Z  INFO namada_apps::node::ledger: Tx WASM compilation cache size not configured, using 1/6 of available memory.
2023-08-09T19:07:13.014172Z  INFO namada_apps::node::ledger: Tx WASM compilation cache size: 4.99 TiB
2023-08-09T19:07:13.014177Z  INFO namada_apps::node::ledger: Block cache size not configured, using 1/3 of available memory.
2023-08-09T19:07:13.014181Z  INFO namada_apps::node::ledger: RocksDB block cache size: 9.98 TiB

Indicate on which release or other PRs this topic is based on

v0.20.1

Checklist before merging to draft

• I have added a changelog
• Git history is in acceptable state

[yito88]

available_memory() in sysinfo v0.27.8 (downgrading at #1775) also returns Byte

[sug0]

nice find! lgtm