disabled some expensive and/or unnecessary clang-tidy checks (#5660)

Running clang-tidy with `--enable-check-profile` provides an overview of
the run-time of each check. This revealed some checks which take a
considerable amount of time which could be disabled.

Here's the times for the checks in question. The times are very similar
across most files:
```
   ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
...
   0.4531 (  4.7%)   0.3906 (  6.1%)   0.8438 (  5.2%)   0.8127 (  5.1%)  misc-unused-using-decls
...
   0.3281 (  3.4%)   0.2344 (  3.7%)   0.5625 (  3.5%)   0.4509 (  2.8%)  modernize-macro-to-enum
...
   0.2188 (  2.2%)   0.2031 (  3.2%)   0.4219 (  2.6%)   0.3621 (  2.3%)  modernize-use-nullptr
```

.clang-tidy

@@ -39,8 +39,11 @@ Checks: >
         -misc-use-anonymous-namespace,
         -modernize-avoid-c-arrays,
         -modernize-deprecated-ios-base-aliases,
+        -modernize-use-nullptr,
         -misc-include-cleaner,
+        -misc-unused-using-decls,
         -modernize-loop-convert,
+        -modernize-macro-to-enum,
         -modernize-raw-string-literal,
         -modernize-replace-auto-ptr,
         -modernize-return-braced-init-list,

clang-tidy.md

@@ -160,6 +160,8 @@ To be evaluated (need to enable explicitly).
 
 These apply to codebases which use later standards then C++11 (C++17 is used when building with Qt6) so we cannot simply apply them.
 
+### Disabled for performance reasons
+
 `portability-std-allocator-const`<br/>
 
 Only necessary for code which is exclusively compiled with `libc++`. Also disabled for performance reasons - see https://github.com/llvm/llvm-project/issues/57527#issuecomment-1237935132.
@@ -183,3 +185,15 @@ We are currently using our own `naming.json` to enforce naming schemes. Also dis
 `portability-simd-intrinsics`<br/>
 
 We are not using SIMD instructions and it suggests to use `std::experiemental::` features which might not be commonly available. Also disabled for performance reasons - see https://github.com/llvm/llvm-project/issues/57527#issuecomment-1237935132.
+
+`modernize-macro-to-enum`<br/>
+
+It does not seem to produce any warnings for us (needs to be investigated) and it is one of the more expensive checks.
+
+`misc-unused-using-decls`
+
+This is the most expensive check for several files and it is providing much in terms of code quality. Reported upstream as https://github.com/llvm/llvm-project/issues/72300.
+
+`modernize-use-nullptr`
+
+This is already covered by the `-Wzero-as-null-pointer-constant` compiler warning so there is no need for an additional check.