Fixes a small issue I noticed while reading through the tutorial.

This PR removes `vector.extractelement` and `vector.insertelement` ops
from the code base in favor of the `vector.extract` and `vector.insert`
counterparts.

See RFC:
https://discourse.llvm.org/t/rfc-psa-remove-vector-extractelement-and-vector-insertelement-ops-in-favor-of-vector-extract-and-vector-insert-ops

Fixed some bugs in documentation. Add CallOpInterfaceHandle to the
arguments of ChangeCallTargetOp, after doing so the section described in
the documentation works correctly, Otherwise the following code reports
an error.
```
// Cast to our new type.
 %casted = transform.cast %call : !transform.any_op to !transform.my.call_op_interface
// Using our new operation.
 transform.my.change_call_target %casted, "microkernel" : !transform.my.call_op_interface
```

Fixed error code in example.In addition to this, the content in the documentation has been improved by adding links to the code repository.

In the transform dialect tutorial chapter 1, there were some errors that
prevented the example from running. This PR fixes them.

---------

Co-authored-by: Renato Golin <rengolin@systemcall.eu>

RFC:
https://discourse.llvm.org/t/rfc-deprecate-linalg-elemwise-unary-and-elemwise-binary/87144

Remove the two operations and fix the tests by:
* Cleaning simple operation tests of the old ops
* Changing `linalg.elemwise_{u|bi}nary` with `linalg.{exp|add}` on
transform tests
* Changing some of the tests with `linalg.elementwise` instead, to
broaden test coverage
* Surgically removing the `elemwise_*` part in the Python tests
* Update MLIR transform examples (text and tests) with
`linalg.elementwise` instead

Nothing else changed.

These have been deprecated for over two years now in favor of free
functions.

See the relevant discourse thread:

https://discourse.llvm.org/t/preferred-casting-style-going-forward/68443
and the deprecation notice: https://mlir.llvm.org/deprecation/.

References to headings need to be preceded with a slash. Also,
references to headings on the same page do not need to contain the name
of the document (omitting the document name means if the name changes
the links will still be valid).

I double checked the links by building [the
website](https://github.com/llvm/mlir-www):

```shell
./mlir-www-helper.sh --install-docs ../llvm-project website
cd website && hugo serve
```