This commit ports [EscapeAnalysis.jl](https://github.com/aviatesk/EscapeAnalysis.jl) into Julia base.
You can find the documentation of this escape analysis at [this GitHub page](https://aviatesk.github.io/EscapeAnalysis.jl/dev/)[^1].

[^1]: The same documentation will be included into Julia's developer
      documentation by this commit.

This escape analysis will hopefully be an enabling technology for various
memory-related optimizations at Julia's high level compilation pipeline.
Possible target optimization includes alias aware SROA (#43888),
array SROA (#43909), `mutating_arrayfreeze` optimization (#42465),
stack allocation of mutables, finalizer elision and so on[^2].

[^2]: It would be also interesting if LLVM-level optimizations can consume
      IPO information derived by this escape analysis to broaden
      optimization possibilities.

The primary motivation for porting EA by this PR is to check its impact
on latency as well as to get feedbacks from a broader range of developers.
The plan is that we first introduce EA to Julia Base by this commit, and
then merge the depending PRs built on top of this commit later.

This commit simply defines EA inside Julia base compiler and enables the
existing test suite with it. In this commit we don't run EA at all, and
so this commit shouldn't affect Julia-level compilation latency.

In the depending PRs, EA will run in two stages:
- `IPO EA`: run EA on pre-inlining state to generate IPO-valid cache
- `Local EA`: run EA on post-inlining state to generate local escape
              information used for various optimizations

In order to integrate `IPO EA` with our compilation cache system,
this commit also implements a new `CodeInstance.argescapes` field that
keeps the IPO-valid cache generated by `IPO EA`.