Eliminate the `indent` argument for functions which are always called
with `indent(0)`.

The `insertBits` templated function generated by DecoderEmitter is
called with variable `tmp` of type `TmpType` which is:

```
using TmpType = std::conditional_t<std::is_integral<InsnType>::value, InsnType, uint64_t>;
```

That is, `TmpType` is always an integral type. Change the generated
`insertBits` to be valid only for integer types, and eliminate the
unused `insertBits` function from `DecoderUInt128` in
AMDGPUDisassembler.h

Additionally, drop some of the requirements `InsnType` must support as
they no longer seem to be required.

Rename `getXYZInstructionsByEnumValue()` to just `getXYZInstructions`
and drop the `ByEnumValue` in the name.

Add a convenience wrapper struct for the `bit_value_t` enum type to host
various constructors, query, and printing support. Also refactor related
code in several places. In `getBitsField`, use `llvm::append_range` and
`SmallVector::append()` and eliminate manual loops. Eliminate
`emitNameWithID` and instead use the `operator <<` that does the same
thing as this function. Have `BitValue::getValue()` (replacement for
`Value`) return std::optional<> instead of -1 for unset bits. Terminate
with a fatal error when a decoding conflict is encountered.

Add option `use-fn-table-in-decode-to-mcinst` to use a table of function
pointers instead of a switch case in the generated `decodeToMCInst`
function.

When the number of switch cases in this function is large, the generated
code takes a long time to compile in release builds. Using a table of
function pointers instead improves the compile time significantly (~3x
speedup in compiling the code in a downstream target). This option will
allow targets to opt into this mode if they desire for better build
times.

Tested with `check-llvm-mc` with the option enabled by default.

Also assign variable names to different elements of `OpMap` for better
readibility, and eliminate `NumberedEncodingsRef` as `std::vector` will
automatically get converted to an `ArrayRef`.

TryDecode/CheckPredicate/SoftFail MCD ops are not used by many targets.
Track the set of opcodes that were emitted and emit code for handling
TryDecode/CheckPredicate/SoftFail ops when decoding only if there were
emitted. This is purely eliminating dead code in the generated
`decodeInstruction` function.

This results in the following reduction in the size of the Disassembler
.so files with a release x86_64 release build on Linux:

```
Target                                                   Old Size        New Size  %  reduction
build/lib/libLLVMAArch64Disassembler.so.21.0git             256656          256656          0.00
build/lib/libLLVMAMDGPUDisassembler.so.21.0git              813000          808168          0.59
build/lib/libLLVMARCDisassembler.so.21.0git                  44816           43536          2.86
build/lib/libLLVMARMDisassembler.so.21.0git                 281744          278808          1.04
build/lib/libLLVMAVRDisassembler.so.21.0git                  36040           34496          4.28
build/lib/libLLVMBPFDisassembler.so.21.0git                  26248           23168         11.73
build/lib/libLLVMCSKYDisassembler.so.21.0git                 55960           53632          4.16
build/lib/libLLVMHexagonDisassembler.so.21.0git             115952          113416          2.19
build/lib/libLLVMLanaiDisassembler.so.21.0git                24360           21008         13.76
build/lib/libLLVMLoongArchDisassembler.so.21.0git            58584           56168          4.12
build/lib/libLLVMM68kDisassembler.so.21.0git                 57264           53880          5.91
build/lib/libLLVMMSP430Disassembler.so.21.0git               28896           28440          1.58
build/lib/libLLVMMipsDisassembler.so.21.0git                123128          120568          2.08
build/lib/libLLVMPowerPCDisassembler.so.21.0git              80656           78096          3.17
build/lib/libLLVMRISCVDisassembler.so.21.0git               154080          150200          2.52
build/lib/libLLVMSparcDisassembler.so.21.0git                42040           39568          5.88
build/lib/libLLVMSystemZDisassembler.so.21.0git              97056           94552          2.58
build/lib/libLLVMVEDisassembler.so.21.0git                   83944           81352          3.09
build/lib/libLLVMWebAssemblyDisassembler.so.21.0git          25280           25280          0.00
build/lib/libLLVMX86Disassembler.so.21.0git                2920624         2920624          0.00
build/lib/libLLVMXCoreDisassembler.so.21.0git                48320           44288          8.34
build/lib/libLLVMXtensaDisassembler.so.21.0git               42248           35840         15.17
```

Automated with clang-tidy -fix -checks=-*,modernize-use-default-member-init

Print DecodeIdx associated with Decode MCD ops in the generated decoder
tables. This can help in debugging decode failures by first mapping the
Op -> DecodeIdx and then inspecting the code in `decodeToMCInst`
associated with that DecodeIdx.