* ethdb: use pebble
Co-authored-by: Gary Rong <garyrong0905@gmail.com>

foo

update

* apply suggested changes

* flags: go format

node: fix ddir lookup mistake

accounts/abi/bind: fix go.mod replacement for generated binding

deps: update pebble + with fix 32-bit build

* ethdb/pebble: respect max memtable size

* core/rawdb, ethdb: enable pebble on non-32bit platforms only

* core/rawdb: fix build tags, fix some review concerns

* core/rawdb: refactor methods for database opening

* core/rawdb: remove erroneous build tag

* cmd/geth: fix the flag default handling + testcase

* cmd/geth: improve testing regarding custom backends

* ethdb/pebble, deps: update pebble dependency

* core/rawdb: replace method with Open

* ethdb/pebble: several updates for pebble (#49)

* ethdb/pebble: fix size count in batch

* ethdb/pebble: disable seek compaction

* ethdb/pebble: more fixes

* ethdb, core, cmd: polish and fixes (#50)

* cmd/utils, core/rawdb, ethdb/pebble: address some review concerns

* Update flags.go

* ethdb/pebble: minor refactors

* ethdb/pebble: avoid copy on batch replay

* ethdb: fix compilation flaw

* cmd: fix test fail due to mismatching error message

* cmd/geth, node: rename backingdb to db.engine

---------
Co-authored-by: Jared Wasinger <j-wasinger@hotmail.com>
Co-authored-by: rjl493456442 <garyrong0905@gmail.com>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>