[clangd] support expanding `decltype(expr)`
Enable the existing tweak `ExpandAutoType` to expand
`decltype(expr)`, e.g.
```
decltype(0) i;
```
will expand to
```
int i;
```
Therefore, rename the tweak `ExpandAutoType` to `ExpandDeducedType`.
This patch also fixes some nits,
* avoid replacing reference to a function
* avoid replacing array types and reference to an array
Fixes https://github.com/clangd/clangd/issues/1456
Reviewed By: sammccall
Differential Revision: https://reviews.llvm.org/D141226
13 files changed: