fix(TM): Initialized strain IP data with Bu

As titled, this MR makes ThermoMechanics process initialize the initial strain with the value computed from initial displacement, i.e. \mathbf \varepsilon_0=\mathrm{B}\mathbf{u}_0. After this change, all mechanical process related processes initialize the initial strain with \mathbf \varepsilon_0=\mathrm{B}\mathbf{u}_0.

1. Feature description was added to the changelog
2. Tests covering your feature were added?
3. Any new feature or behaviour change was documented?