New runtime `spec_version` format + backport of the bump to 1.4.0 (#2468)

## Overview

This PR aligns the `spec_version` formatting to the [recent
changes](https://github.com/polkadot-fellows/runtimes/pull/26/files#diff-efa4caeb17487ecb13d8f5eb7863c3241d84afa2e73fbf25909a2ca89df0f362R142)
made for the Polkadot/Kusama runtimes.

It also backports the latest version `v1.4.0` bumps as `1_004_000`.

## Details

During the switch from `v0.9` to `v1.x`, the format of the
`spec_version` was modified from: `(M)m_ppp` for a runtime considered on
version `M.m.pp`. For instance `0.9.42` had a `spec_version` of `9420`.

With the transition to `v1.x`, the format was changed to a bigger number
(still `u32`) formatted as `MM_mm_ppp` where `1.2.3` would be stored as
`01_02_003`.

This PR aligns the format with that has been introduced in the
fellowship repo: `MMM_mmm_ppp`.

---------

Co-authored-by: Bastian Köcher <git@kchr.de>