feat: release version 5.2.0

This release includes the following changes:
- Bindings for ICU 77.
- Robotic code change procedures.
- Version files moved to top-level.
- Updated version support matrix.
- Limited parallelism of builds.
- New buildenv (1.82.0) and ToT builder.
- Container for building ICU against `main`.
- Fix for config file extension.

This commit was created by an automated coding assistant, with human
supervision.

feat: release version 5.1.0

This release includes the following changes:
- Add bindings for ICU 77.
- Add procedures for robotic code changes.
- Update the version support matrix.
- Limit the parallelism of builds.
- Create a container for building ICU against `main`.
- Fix the config file extension.

This commit was created by an automated coding assistant, with human
supervision.

Merge branch 'filmil-mascot'

chore: update the release to 4.2.3

Fix a scoping bug.

Issue: #282

feat: support UDataMemory::open

This should be a better way to manage the resource
memory, as resources created by `open` are memory
mapped on demand.

Some memory-constrained execution environments may
care.

Updates the `rust_icu` source for ICU 73.1

This time around, no changes to the tests were needed, it seems.
Updates the `rust_icu` version to 4.0.0.

Issue: #270

Adds ICU v73.1 to the built images

At the same time, v70.1 is no longer supported.

I'll try to have the version numbering schema reflect
the latest version of ICU that is supported. So, at
this time, we will upgrade the buildenv to
`buildenv-1.73.0`.

Issue: #270

Uprev rust_icu to 3.0.0

- 3.0.0 brings support for ICU 72.1
- Dropped support for ICU 68.1, and ICU 69.1, they are out of support
  window.
- Dropped `rust_icu` 0.5, it is out of support window.

Fixes: #258

Uprev the versioning to 2.0.3

This change makes it possible to release the recent bugfixes,
such as #244

Start using buildenv 1.4.3

- The new buildenv supports ICU 71.1
- Ran `make static-bindgen` for ICU 71.1.
- Ran `make uprev` to uprev rust_icu to 2.0.2.
- Added the test workflow for ICU 71.  Not evicting ICU 68 yet, since
  we didn't update the major version number.

Issue: #293