[Mosaic TPU] Support 1D concat: set implicit_dim to kSecondMinor to treat 1D (N,) as (1, N) and then tile it as (1, 128)

[Mosaic TPU] Support 1D concat: set implicit_dim to kSecondMinor to treat 1D (N,) as (1, N) and then tile it as (1, 128) #4449