[CIR][NFC] Use TableGen to generate LLVM lowering patterns (#159390)

Most lowering patterns have exactly the same class declaration with
different names and different `matchAndRewrite` implementations, yet
their declaration occupies near 1000 lines of code in `LowerToLLVM.h`,
making this file difficult to read and boring to maintain. In this
patch, I migrate their declarations to be generated from `CIROps.td`
using `clang-tblgen`. Some extra `CIR_Op` TableGen fields are introduced
to help this:

- The `CIR_Op` class now defines a `bit` field `hasLLVMLowering` which
defaults to `true`. If its value is `true`, `clang-tblgen` would
generate an LLVM lowering pattern declaration for the operation.

- Some LLVM lowering patterns has bounded recursion. This could be
enabled by setting the `isLLVMLoweringRecursive` field in a `CIR_Op`
record to `true`.

- Some LLVM lowering patterns have defined additional class members.
They could be listed in the `extraLLVMLoweringPatternDecl` field.

Note that in the incubator we have a similar TableGen code generator
that generates LLVM lowering code for CIR builtin ops which has a
one-to-one correspondence to LLVM dialect operations. This patch does
NOT try to upstream it.

Some additional noticeable changes made by this patch:

- This patch adds the `dataLayout` member to every LLVM lowering pattern
class to make the job easier for a code generator. In the future we
might want to add more members to the lowering patterns, and we will
need to update the code generator to make such changes.

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