build(solidity): raise TypeScript to 5.9.3 in both packages

[mswilkison]

Stacked on #4204. Raises TypeScript in both solidity packages to 5.9.3,
and adds skipLibCheck.

ecdsa was on ^4.5.4 and random-beacon on ^4.4.3 — 4.5.5 and 4.4.3
resolved, both from 2022. Neither had skipLibCheck, so both were type-checking
their dependencies' declarations as well as their own.

Measured

	before	after
ecdsa	TS 4.5.5 — 1 error	TS 5.9.3 — 1 error
random-beacon	TS 4.4.3 — 33 errors	TS 5.9.3 — 21 errors

No new errors in either. random-beacon drops twelve: the newer compiler
resolves inference the old one gave up on, and skipLibCheck takes three
library declarations out of scope (21 of the 24 without it are ours). The 21
that remain are pre-existing and untouched here.

Suites unchanged:

random-beacon	955 passing / 0 pending / 0 failing
ecdsa	673 passing / 44 pending / 0 failing

Why now

Same reason as threshold-network/tbtc-v2#1068 — it is a prerequisite for
replacing waffle, whichever replacement is chosen:

• viem, abitype and ox declare typescript >= 5.0.4 and their declarations
  do not parse on 4.x at all
• ethers v6 with typechain v8 needs it too: typechain types a contract method as
  TypedContractMethod, and a 4.x compiler cannot resolve a conditional type
  against it

Why 5.9 and not 6 or 7

Not 7. It is the native Go port, and yarn 4.12.0 cannot install it here at
all — yarn applies a builtin compat patch expecting lib/_tsc.js, which the Go
port does not ship, so the install aborts in the fetch step. (Yarn 4.17.1
installs it fine, so that is a yarn bump rather than a TypeScript wait.)

Not 6 yet, but that is the one to watch. 6.0.3 is stable and is what
Hardhat 3 develops against (hardhat@3.11.1 dev-depends on typescript: ~6.0.3), so TypeScript 6 is the version to pair with a Hardhat 3 move — not
something to take early and not 7.

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