feat(ext/kv): key-value store

[losfair]

This commit adds unstable "Deno.openKv()" API that allows to open
a key-value database at a specified path.

[CLAassistant]

All committers have signed the CLA.

[bartlomieju]

Marking as "Request changes" because we're in the middle of refactor to ops in
#18080 and #18210.

Let's keep reviewing this PR, but I want to hold of until weekend with landing this one.

[lucacasonato]

todo:

• test key serialization from/to js (bigint panics right now)
• move selector & cursor parsing logic to rust

[bartlomieju]

LGTM, I read through the source and besides some nitpicks there's nothing standing out.

We can address these nitpicks after the release.

[jsejcksn]

@losfair I see a Deno.Kv#getMany method in the types, but a corresponding method does not exist on an instance at runtime. Was the method a short-lived experiment or am I missing something?

example.ts:

/// <reference lib="deno.unstable" />

const db = await Deno.openKv(":memory:");

console.log(Object.getOwnPropertyNames(Object.getPrototypeOf(db)));

console.log(await db.getMany([]));

await db.close();

% deno --version
deno 1.32.0 (release, aarch64-apple-darwin)
v8 11.2.214.9
typescript 5.0.2

% deno check example.ts

% echo $?
0

% deno run --unstable example.ts
[
  "constructor",
  "atomic",
  "get",
  "set",
  "delete",
  "list",
  "close"
]
error: Uncaught TypeError: db.getMany is not a function
console.log(await db.getMany([]));
                     ^
    at file:///Users/deno/example.ts:7:22

[losfair]

@jsejcksn fixed in #18410