ledger-tool: Move blockstore commands to blockstore subcommand (solan…

…a-labs#34597)

solana-ledger-tool is a bit of a kitchen sink and currently has
upwards of 30 commands at the top level of the CLI. UI aside, the
contents of ledger-tool/src/main.rs are somewhat cluttered.

To reduce clutter and introduce a more hierarchical structure, this
change introduces a new blockstore subcommand and moves all commands
that only touch the blockstore to a blockstore subcommand. For example,
  solana-ledger-tool slot X 
is now invoked like
  solana-ledger-tool blockstore slot X

However, given how long the tool has existed, support is retained for
calling these old commands without the extra blockstore command. But,
the commands are not listed in the help in order to steer new users to
use the newer calling structure.