module: derive builtinModules from enabled builtin set

[sjungwon03]

Module.builtinModules is expected to contain only builtins accessible
to user code.

During pre-execution, each experimental flag determines whether its
builtin is added to BuiltinModule's user-requirable set via
BuiltinModule.allowRequireByUsers().

Before this change, getAllBuiltinModuleIds() added every scheme-only
builtin to the Module.builtinModules candidate list, including
experimental builtins that had not been added to the user-requirable
set. initializeCJS() then repeated the flag checks and removed
node:dtls, node:quic, node:ffi, and node:vfs.

Derive the scheme-only portion of Module.builtinModules from the
already-established user-requirable set instead. This keeps the list
consistent with the existing require('node:...') access policy and
removes the duplicated filtering in initializeCJS().

Existing scheme-only builtins such as node:test, node:sea, and
node:sqlite remain listed.

Add coverage for Module.builtinModules and require('node:...')
with and without each experimental flag.

Refs: #56185
Refs: #56870
Refs: #63158

[nodejs-github-bot]

Review requested:

• @nodejs/loaders
• @nodejs/startup

[sjungwon03]

Follow-up: the focused test assumed that node:sqlite is available in
all builds. Slim builds can be compiled without SQLite, so the test now
only verifies node:sqlite when common.hasSQLite is true.

node:test and node:sea remain covered unconditionally.