Eliminate the `lldb_private::dwarf` namespace, in favor of using
`llvm::dwarf` directly. The latter is shorter, and this avoids ambiguity
in the ABI plugins that define a `dwarf` namespace inside an anonymous
namespace.

Not that we ever do that, because this is unused code, but if someone
was debugging lldb I guess they'd call this.

Was missed in https://github.com/llvm/llvm-project/pull/145645

Relates to https://github.com/llvm/llvm-project/issues/135208

Follow-up to
https://github.com/llvm/llvm-project/pull/145645#discussion_r2174948997

There's no need for this variable to be declared at the function-level.
We reset it in all the cases where it's used anyway.

This patch just inlines the usage of the variable entirely.

This PR introduces support for the DWARF64 format, enabling handling of
64-bit DWARF sections as defined by the DWARF specification. The update
includes adjustments to header parsing and modification of form values
to accommodate 64-bit offsets and values.
Also Added the testcase to verify the DWARF64 format.

9de73b20404f0b2db1cbf70d164cfe0789d5bb94 lands a fix to DWARFTypePrinter that is used by lldb in this change.

This reverts commit f06c187799d910fd3ac3e9106397e5eecff9f265.

Temporary revert: there is https://github.com/llvm/llvm-project/pull/117239 that is suppose to fix the issue.
Reverting to keep things rolling.

This is a reland of https://github.com/llvm/llvm-project/pull/112811.
Fixed the bot breakage by running ld.lld explicitly.

This reverts commit 94d100f2ba81c2bf0ef495f68d66ba8c94c71d2a.

Reverted because of greendragon failure on the incremental arm64 bot

******************** TEST 'lldb-shell :: SymbolFile/DWARF/x86/simplified-template-names.cpp' FAILED ********************
Exit Code: 1

RUN: at line 7: /Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/lldb-build/bin/clang --driver-mode=g++ --target=specify-a-target-or-use-a-_host-substitution --target=x86_64-pc-linux -g -gsimple-template-names /Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/llvm-project/lldb/test/Shell/SymbolFile/DWARF/x86/simplified-template-names.cpp -o /Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/lldb-build/tools/lldb/test/Shell/SymbolFile/DWARF/x86/Output/simplified-template-names.cpp.tmp

/Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/lldb-build/bin/clang --driver-mode=g++ --target=specify-a-target-or-use-a-_host-substitution --target=x86_64-pc-linux -g -gsimple-template-names /Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/llvm-project/lldb/test/Shell/SymbolFile/DWARF/x86/simplified-template-names.cpp -o /Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/lldb-build/tools/lldb/test/Shell/SymbolFile/DWARF/x86/Output/simplified-template-names.cpp.tmp
ld: warning: -m is obsolete
ld: unknown option: --hash-style=gnu
clang: error: linker command failed with exit code 1 (use -v to see invocation)

This is the second half of
https://github.com/llvm/llvm-project/pull/90008.

Essentially, it replaces the work of resolving template types when we
just need the qualified names with walking the DIE tree using
`DWARFTypePrinter`.

### Result
For an internal target, the time spent on `expr *this` for the first
time reduced from 28 secs to 17 secs.

This FORM already has support within LLDB to be parsed as a 16-byte
BLOCK, and all that is left to properly support it in the DWARFParser is
to add it to some enums.

With this, I can debug programs that use libstdc++.so.6.0.33 built with
GCC.