With LDBG(), the code isn't guarded in release mode, even if the optimizer
will remove it because there is a `if (false)` statement. We need the
function declaration to be there at minima.

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

- try_emplace(Key) is shorter than insert({Key, nullptr}).
- try_emplace performs value initialization without value parameters.
- We overwrite values on successful insertion anyway.

Current inliner disables inlining when the caller is in a region with
single block trait, while the callee function contains multiple blocks.
the SingleBlock trait is used in operations such as do/while loop, for
example fir.do_loop, fir.iterate_while and fir.if. Typically, calls within
loops are good candidates for inlining. However, functions with multiple
blocks are also common. for example, any function with "if () then
return" will result in multiple blocks in MLIR.

This change gives the flexibility of a customized inliner to handle such
cases.
doClone: clones instructions and other information from the callee
function into the caller function. .
canHandleMultipleBlocks: checks if functions with multiple blocks can be
inlined into a region with the SingleBlock trait.

The default behavior of the inliner remains unchanged.

---------

Co-authored-by: jeanPerier <jean.perier.polytechnique@gmail.com>
Co-authored-by: Mehdi Amini <joker.eph@gmail.com>

I observed that we have the boundary comments in the codebase like:

```
//===----------------------------------------------------------------------===//
// ...
//===----------------------------------------------------------------------===//
```

I also observed that there are incomplete boundary comments. The
revision is generated by a script that completes the boundary comments.

```
//===----------------------------------------------------------------------===//
// ...

...
```

Signed-off-by: hanhanW <hanhan0912@gmail.com>

Discussion at https://discourse.llvm.org/t/inliner-cost-model/2992

This change adds a callback that reports whether inlining
of the particular call site (communicated via ResolvedCall argument)
is profitable or not. The default MLIR inliner pass behavior
is unchanged, i.e. the callback always returns true.
This callback may be used to customize the inliner behavior
based on the target specifics (like target instructions costs),
profitability of the inlining for further optimizations
(e.g. if inlining may enable loop optimizations or scalar optimizations
due to object shape propagation), optimization levels (e.g. -Os inlining
may be quite different from -Ofast inlining), etc.

One of the questions is whether the ResolvedCall entity represents
enough of the context for the custom inlining models to come up with
the profitability decision. I think we can start with this and
extend it as necessary.

---------

Co-authored-by: Mehdi Amini <joker.eph@gmail.com>