bugfix: Fix a bug that caused output without specifying index name

[Karibash]

close #3420

Fixed a bug that caused empty index names to be output when executing the introspect command with auto-generated index names.
This fix is necessary because the specification of the index name is mandatory.

drizzle-orm/drizzle-orm/src/mysql-core/indexes.ts

Lines 102 to 108 in 55231b0

	export function index(name: string): IndexBuilderOn {
	return new IndexBuilderOn(name, false);
	}
	export function uniqueIndex(name: string): IndexBuilderOn {
	return new IndexBuilderOn(name, true);
	}

[Karibash]

@AndriiSherman
Would it be better to make the index names optional, as in pg-core?

drizzle-orm/drizzle-orm/src/pg-core/indexes.ts

Lines 245 to 247 in 55231b0

	export function index(name?: string): IndexBuilderOn {
	return new IndexBuilderOn(false, name);
	}

[Karibash]

@AndriiSherman
I apologize for being persistent, but have you had a chance to look into this?
If you can provide any instructions, I will make the necessary corrections.

[AndriiSherman]

Please fix conflicts and I'll merge this PR! thanks for your work!

[Karibash]

fixed it