…gnment (#52182)

The llvm optimizations may increase alignment beyond the initial
MAX_ALIGN. This pool's alignment was previously only `sizeof(struct {
atomic<int> RefCount; size_t Length; char Data[]; })` however,
potentially resulting in segfaults at runtime.

Fixes #52118. Should make CI much happier.

(cherry picked from commit a65bc9a)

(cherry picked from commit 72cd63c)

Backported PRs:
- [x] #51213 <!-- Wait for other threads to finish compiling before
exiting -->
- [x] #51520 <!-- Make allocopt respect the GC verifier rules with non
usual address spaces -->
- [x] #51598 <!-- Use a simple error when reporting sysimg load
failures. -->
- [x] #51757 <!-- fix parallel peakflop usage -->
- [x] #51781 <!-- Don't make pkgimages global editable -->
- [x] #51848 <!-- allow finalizers to take any locks and yield during
exit -->
- [x] #51847 <!-- add missing wait during Timer and AsyncCondition close
-->
- [x] #50824 <!-- Add some aliasing warnings to docstrings for mutating
functions in Base -->
- [x] #51885 <!-- remove chmodding the pkgimages -->
- [x] #50207 <!-- [devdocs] Improve documentation about building
external forks of LLVM -->
- [x] #51967 <!-- further fix to the new promoting method for
AbstractDateTime subtraction -->
- [x] #51980 <!-- macroexpand: handle const/atomic struct fields
correctly -->
- [x] #51995 <!-- [Artifacts] Pass artifacts dictionary to
`ensure_artifact_installed` dispatch -->
- [x] #52098 <!-- Fix errors in `sort` docstring -->
- [x] #52136 <!-- Bump JuliaSyntax to 0.4.7 -->
- [x] #52140 <!-- Make c func `abspath` consistent on Windows. Fix
tracking path conversion. -->
- [x] #52009 <!-- fix completion that resulted in startpos of 0 for `\\
-->
- [x] #52192 <!-- cap the number of GC threads to number of cpu cores
-->
- [x] #52206 <!-- Make have_fma consistent between interpreter and
compiled -->
- [x] #52027 <!-- fix Unicode.julia_chartransform for Julia 1.10 -->
- [x] #52217 <!-- More helpful error message for empty `cpu_target` in
`Base.julia_cmd` -->
- [x] #51371 <!-- Memoize `cwstring` when used for env lookup /
modification on Windows -->
- [x] #52214 <!-- Turn Method Overwritten Error into a PrecompileError
-- turning off caching -->
- [x] #51895 <!-- Devdocs on fixing precompile hangs, take 2 -->
- [x] #51596 <!-- Reland "Don't mark nonlocal symbols as hidden"" -->
- [x] #51834 <!-- [REPLCompletions] allow symbol completions within
incomplete macrocall expression -->
- [x] #52010 <!-- Revert "Support sorting iterators (#46104)" -->
- [x] #51430 <!-- add support for async backtraces of Tasks on any
thread -->
- [x] #51471 <!-- Fix segfault if root task is NULL -->
- [x] #52194 <!-- Fix multiversioning issues caused by the parallel llvm
work -->
- [x] #51035 <!-- refactor GC scanning code to reflect jl_binding_t are
now first class -->
- [x] #52030 <!-- Bump Statistics -->
- [x] #52189 <!-- codegen: ensure i1 bool is widened to i8 before
storing -->
- [x] #52228 <!-- Widen diagonal var during `Type` unwrapping in
`instanceof_tfunc` -->
- [x] #52182 <!-- jitlayers: replace sharedbytes intern pool with one
that respects alignment -->

Contains multiple commits, manual intervention needed:
- [ ] #51092 <!-- inference: fix bad effects for recursion -->

Non-merged PRs with backport label:
- [ ] #52196 <!-- Fix creating custom log level macros -->
- [ ] #52170 <!-- fix invalidations related to `ismutable` -->
- [ ] #51479 <!-- prevent code loading from lookin in the versioned
environment when building Julia -->