Added `ColumnType::Blob` #650

Job	Run time
Clippy	1m 3s
Compile MySQL (live/mysql)	1m 5s
Compile Postgres (live/postgres)	1m 7s
Compile MySQL (discovery/mysql)	1m 8s
Compile SQLite (live/sqlite)	1m 13s
Compile Postgres (discovery/postgres)	1m 11s
Compile MySQL (writer/mysql)	1m 3s
Rustfmt	11s
Compile SQLite (discovery/sqlite)	1m 4s
Compile Postgres (writer/postgres)	1m 0s
Compile SQLite (writer/sqlite)	58s
Unit Test	1m 25s
MariaDB (10.6, live/mysql)	49s
MySQL (8, live/mysql)	57s
MariaDB (10.6, discovery/mysql)	1m 2s
MySQL (8, discovery/mysql)	56s
MariaDB (10.6, writer/mysql)	40s
MySQL (8, writer/mysql)	52s
MySQL (5.7, live/mysql)	50s
MySQL (5.7, discovery/mysql)	47s
MySQL (5.7, writer/mysql)	46s
Postgres (14.4, live/postgres)	1m 0s
Postgres (14.4, discovery/postgres)	59s
Postgres (14.4, writer/postgres)	1m 3s
SQLite (live/sqlite)	22s
SQLite (discovery/sqlite)	22s
SQLite (writer/sqlite)	18s
	24m 11s

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