Identified with readability-redundant-control-flow.

This is a part of effort to have better const correctness in TableGen
backends:


https://discourse.llvm.org/t/psa-planned-changes-to-tablegen-getallderiveddefinitions-api-potential-downstream-breakages/81089

Use const record pointers in TableGen/Common files.

This is a part of effort to have better const correctness in TableGen
backends:


https://discourse.llvm.org/t/psa-planned-changes-to-tablegen-getallderiveddefinitions-api-potential-downstream-breakages/81089

Instead, move it to CodeGenTarget class, and use it in both
PatternParser and SearchableTableEmitter.

- Add class `CodeGenIntrinsicMap` for on-demand creation of  
  `CodeGenIntrinsic`.
- Add class `CodeGenIntrinsicContext` to capture global information
  required to build `CodeGenIntrinsic` objects.
- Adopt GlobalISel PatternParser and SearchableTableEmitter to use it.

CodeGenIntrinsic changes:
  - Use `const` Record pointers, and `StringRef` when possible.
  - Default initialize several fields with their definition instead of in
 the constructor.
- Simplify various string checks in the constructor using StringRef
starts_with()/ends_with() functions.
- Eliminate first argument to `setDefaultProperties` and use `TheDef`
class member instead.

IntrinsicEmitter changes:
  - Emit `namespace llvm::Intrinsic` instead of nested namespaces.
  - End generated comments with a .
  - Use range based for loops, and early continue within loops.
  - Emit `static constexpr` instead of `static const` for arrays.
- Change `compareFnAttributes` to use std::tie() to compare intrinsic
attributes and return a default value when all attributes are equal.

STLExtras:
  - Add std::replace wrapper which takes a range.

Reland of cfa0833ccc7450a322e709583e894e4c96ce682e