* common/fdlimit: build on DragonflyBSD

* review feedback

* core/vm: use fixed uint256 library instead of big

* core/vm: remove intpools

* core/vm: upgrade uint256, fixes uint256.NewFromBig

* core/vm: use uint256.Int by value in Stack

* core/vm: upgrade uint256 to v1.0.0

* core/vm: don't preallocate space for 1024 stack items (only 16)

Co-authored-by: Martin Holst Swende <martin@swende.se>

* replace gosigar with gopsutil

* removed check for whether GOOS is openbsd

* removed accidental import of runtime

* potential fix for difference in units between gosig and gopsutil

* fixed lint error

* remove multiplication factor

* uses cpu.ClocksPerSec as the multiplication factor

* changed dependency from shirou to renaynay (#20)

* updated dep

* switching back from using renaynay fork to using upstream as PRs were merged on upstream

* removed empty line

* optimized imports

* tidied go mod

golang-lru is now a go module, and the upgrade corrects a couple
of minor issues. In particular, the library could crash if you inserted
nil into an LRU cache.

This revision of go-duktype fixes the following warning

```
duk_logging.c: In function ‘duk__logger_prototype_log_shared’:
duk_logging.c:184:64: warning: ‘Z’ directive writing 1 byte into a region of size between 0 and 9 [-Wformat-overflow=]
  184 |  sprintf((char *) date_buf, "%04d-%02d-%02dT%02d:%02d:%02d.%03dZ",
      |                                                                ^
In file included from /usr/include/stdio.h:867,
                 from duk_logging.c:5:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:36:10: note: ‘__builtin___sprintf_chk’ output between 25 and 85 bytes into a destination of size 32
   36 |   return __builtin___sprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   37 |       __bos (__s), __fmt, __va_arg_pack ());
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

The new goja version supports the 'escape' and 'unescape' built-in functions.
This fixes #20693

* signer: replace otto with goja

* go.mod: remove Otto

This replaces the JavaScript interpreter used by the console with goja,
which is actively maintained and a lot faster than otto. Clef still uses otto
and eth/tracers still uses duktape, so we are currently dependent on three
different JS interpreters. We're looking to replace the remaining uses of otto
soon though.

* p2p/dnsdisc: add support for enode.Iterator

This changes the dnsdisc.Client API to support the enode.Iterator
interface.

* p2p/dnsdisc: rate-limit DNS requests

* p2p/dnsdisc: preserve linked trees across root updates

This improves the way links are handled when the link root changes.
Previously, sync would simply remove all links from the current tree and
garbage-collect all unreachable trees before syncing the new list of
links.

This behavior isn't great in certain cases: Consider a structure where
trees A, B, and C reference each other and D links to A. If D's link
root changed, the sync code would first remove trees A, B and C, only to
re-sync them later when the link to A was found again.

The fix for this problem is to track the current set of links in each
clientTree and removing old links only AFTER all links are synced.

* p2p/dnsdisc: deflake iterator test

* cmd/devp2p: adapt dnsClient to new p2p/dnsdisc API

* p2p/dnsdisc: tiny comment fix

Also remove dependency on gopkg.in/check.v1 in tests.