refactor(LinearAlgebra/Matrix/BilinearForm): Derive BilinearForm results from SesquilinearForm (#9485)

Give definitions in `LinearAlgebra/Matrix/BilinearForm` in terms of the equivalent definitions in `LinearAlgebra/Matrix/SesquilinearForm` and derive the `BilinearForm` results as effectively special cases of the equivalent results in `SesquilinearForm`. This reduces the length of  `LinearAlgebra/Matrix/BilinearForm` by over 100 lines.

The aim is to:

* Clarify how results in `BilinearForm` relate to results in `SesquilinearForm`
* Reduce duplication of argument between the two files
* Validate that the results in `SesquilinearForm` are sufficiently general to provide the results in `BilinearForm` in their existing form - in fact, some loosening of the hypothesis in `SesquilinearForm` is required. Further loosening was already applied in #9475



Co-authored-by: Christopher Hoskin <mans0954@users.noreply.github.com>
Co-authored-by: Christopher Hoskin <christopher.hoskin@overleaf.com>

Author: mans0954