Migration CLI --from/--to options do not work with custom migration file names.

[slnz00]

Describe the bug
When using --from or --to cli options a Migration prefix gets appended to the beginning of the given file name. CLI crashes when the previously mentioned options are used with custom migration names.

Migrator.ts#L139

Stack trace

Error: Unable to find migration: Migration20200928151522-migration
at Umzug.<anonymous> (mikro-orm-graphql-example-master/node_modules/umzug/lib/index.js:536:41)
at Umzug.tryCatcher (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/util.js:16:23)
at Promise._settlePromiseFromHandler (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:547:31)
at Promise._settlePromise (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:604:18)
at Promise._settlePromise0 (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:649:10)
at Promise._settlePromises (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:729:18)
at Promise._fulfill (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:673:18)
at Promise._resolveCallback (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:466:57)
at Promise._settlePromiseFromHandler (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:559:17)
at Promise._settlePromise (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:604:18)
at Promise._settlePromise0 (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:649:10)
at Promise._settlePromises (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:729:18)
at Promise._fulfill (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:673:18)
at Promise._resolveCallback (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:466:57)
at Promise._settlePromiseFromHandler (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:559:17)
at Promise._settlePromise (mikro-orm-graphql-example-master/node_modules/bluebird/js/release/promise.js:604:18)

To Reproduce
Steps to reproduce the behavior:

1. Use a custom migration file name generator (Configuration.migrations.fileName). E.g.: (timestamp: string) => '${timestamp}-migration'
2. Generate at least 2 migrations. (migration:create)
3. Apply the migrations. (migration:up)
4. Revert to the first migration. (migration:down --to [first-migration.ts])

Expected behavior
Migrations should be reverted based on the given --from, --to options.

Additional context

Versions

Dependency	Version
node	14.11.0
typescript	3.9.7
mikro-orm	4.0.5
pg	8.2.1