feat(ring_theory/ideal/nc_jacobson_radical): Jacobson radical of noncommutative ring

[haruhisa-enomoto]

Define the Jacobson radical of a ring as the intersection of all maximal left ideals, and prove basic properties: famous equivalent conditions for an element in a ring to be contained in the Jacobson radical, and the Jacobson radical coincides with the intersection of all maximal right ideals.

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