Strengthen `tac_specialize_assert` to put the result in the intuitionistic context.
The result of `iSpecialize ("H" with "[H1 .. Hn]")` was always put in the spatial context. This commit strenghtens this tactic by putting the result in the intuitionistic context if the following conditions hold: 1. The hypothesis `H` is persistent. 2. All the hypotheses `H1 .. Hn` are intuitionistic (or similarly, in case `[-H1 .. Hn]` is used, if all remaining hypotheses are intuitionistic). 3. If the pattern `[> ..]` for adding a modality is not used.