Also removes the code to enforce those limits, including the
`-datacarrier` and `-datacarriersize` config options.
These limits are easily bypassed by both direct submission to miner
mempools (e.g. MARA Slipstream), and forks of Bitcoin Core that do not
enforce them (e.g. Libre Relay). Secondly, protocols are bypassing them
by simply publishing data in other ways, such as unspendable outputs and
scriptsigs.
The *form* of datacarrier outputs remains standardized: a single
OP_Return followed by zero or more data pushes; non-data opcodes remain
non-standard.
In the functional tests there are lots of cases where we assert != which
this new util will replace, we also are adding the imports and the new assertion
The weight unit is merely a consensus rule detail and is largely
irrelevant for fee-rate calculations and mempool policy rules (e.g. for
package relay and TRUC limits), so there doesn't seem to be any value of
using a granularity that we can't even guarantee to reach exactly
anyway.
Switch to the more natural unit of vsize instead, which simplifies both
the padding implementation and the current tests that take use of this
padding. The rather annoying multiplications by `WITNESS_SCALE_FACTOR`
can then be removed and weird-looking magic numbers like `4004` can be
replaced by numbers that are more connected to actual policy limit
constants from the codebase, e.g. `1001` for exceeding
`TRUC_CHILD_MAX_VSIZE` by one.
Keep mentions of v3 in debug strings to help people who might not know
that TRUC is applied when version=3.
Also keep variable names in tests, as it is less verbose to keep v3 and v2.
