fix(perf): do not list network interfaces when loading config definitions

[azchohfi]

Related: #10084 (Windows shims start node once per call) and #10096
(arborist and pacote on first use). Each removes a different part of npm's start-up cost; they
touch different files and the savings add up.

Summary

@npmcli/config/lib/definitions/definitions.js builds the allowed values of local-address at
module load:

'local-address': new Definition('local-address', {
  default: null,
  type: getLocalAddresses(),   // Object.values(os.networkInterfaces())...

So every npm command, npm --version included, enumerates the machine's network interfaces before
it does anything else. On Windows, os.networkInterfaces() goes through GetAdaptersAddresses and
takes about 7.5 ms on the test machine; it grows with VPN and virtual adapters. The list is needed
only when a local-address value is validated, which almost no command does. bin/npx-cli.js
also reads every definition's type to find boolean switches, so npx builds the list too.

This PR:

1. definitions.js: local-address's type becomes a getter that builds the list on first
   read and memoizes it. hint and usage are given explicitly, so Definition does not read
   type to derive them.
2. definition.js: the constructor copies property descriptors instead of using
   Object.assign, so a getter stays a getter. For data properties the two are the same.
3. index.js, getTypesFromDefinitions: a definition whose type is an accessor becomes an
   accessor in types too. nopt reads types[key] only for keys present in argv, env or npmrc,
   so the list is built only when local-address is actually set.
4. bin/npx-cli.js: skips accessor types when it collects boolean switches. A lazily
   computed type is a list of values, never a switch. It uses no optional chaining, because the
   bin scripts must parse on old Node.

os.networkInterfaces() calls per command go from 1 to 0 for npm --version, npm run <script>
and npx <bin>.

Numbers

• Setup:
  • npm 12.2.0 from npm pack of latest (b317f16), against the same tarball with this commit;
  • official Node.js 26.7.0; Windows 11; i9-14900K;
  • a Dev Drive (ReFS), and the system drive (NTFS, Defender real-time scanning).
• Method: interleaved passes after warm-up; medians in ms; the paired per-pass difference
  with its 95% CI.

Windows 11	passes	before	after	saved
npm --version, Dev Drive	60	119.8	112.3	6.9 (4.7–9.8)
npm --version, system drive	60	149.7	137.9	9.3 (5.9–11.5)
npm run noop (node -e 0), Dev Drive	60	214.7	213.1	10.1 (5.4–15.0)
npm run noop, system drive	60	264.1	255.6	8.2 (0.7–15.3)

A second 60-pass run, in a clean user environment on a quieter machine, agrees: npm --version
saves 7.5 ms (6.7–8.6) on the Dev Drive and 10.4 ms (7.3–11.9) on the system drive; npm run noop,
5.0 ms (2.7–8.1) and 7.6 ms (6.2–9.8).

npx --no-install tsc --version (about 485 ms) is too noisy to resolve 7 ms in 40 passes: 3.0
(−7.3–19.0). A hook on os.networkInterfaces() shows the call gone there too.

The change was also tested on Linux: the call count goes from 1 to 0 and nothing regresses.

Behaviour

• Identical output and exit codes, before and after, on Windows and Linux:
  • npm --version;
  • npm config get local-address with a valid --local-address, an invalid one (the same
    warning and null), and one from npm_config_local_address;
  • npm config ls -l.
• Only change: definitions['local-address'].usage. It was built from the machine's own
  addresses (--local-address <…|…>) and is shown nowhere: no command lists local-address among
  its params, and the docs use typeDescription ("IP Address"). It is now
  --local-address <local-address>.

Tests

New tests, each failing without its change:

• workspaces/config/test/definitions/definitions.js: the interfaces are not listed when the
  definitions load, nor by reading hint/usage. They are listed once on the first type read.
• workspaces/config/test/index.js: getTypesFromDefinitions keeps an accessor type lazy. A
  Config does not read it when the key is not set, and validates against it when it is set.
• test/bin/npx-cli.js: npx does not read a lazily typed definition.

Results on Windows 11, Node 26.7.0:

• node . run test -w workspaces/config: passes, 100% coverage;
• node . run lint: clean;
• node . run test: passes except test/bin/windows-shims.js, test/lib/commands/publish.js
  and test/lib/commands/stage/index.js, which fail the same way on unmodified latest on the
  test machine (a PowerShell profile message, and scripts that call touch).

On Linux, the config workspace passes with 100% coverage.

Composition

• Merges cleanly with fix: start node once per call in the Windows npm/npx shims #10084, with fix(perf): lazy load arborist and pacote in libnpmexec #10096, and with the open libnpmexec
  PRs fix: refresh npx cache for local bin changes #9767, fix(libnpmexec): honor min-release-age-exclude in npx #9768, fix(libnpmexec): honor min-release-age-exclude when resolving specs #9944, fix(exec): don't inherit global config when installing to the npx cache #10042, fix(libnpmexec): escape inferred executable names for selected shell #10044 and fix: skip disconnected orphans in install script checks #10068.
• fix(powershell): avoid evaluating CLI paths as source #10058 also edits workspaces/config/lib/index.js and workspaces/config/test/index.js;
  the two merge automatically.