[security] transport.Controller{} and transport.Transport{} security and performance improvements (#564)

* cache transports in controller by privkey-generated pubkey, add retry logic to transport requests

Signed-off-by: kim <grufwub@gmail.com>

* update code comments, defer mutex unlocks

Signed-off-by: kim <grufwub@gmail.com>

* add count to 'performing request' log message

Signed-off-by: kim <grufwub@gmail.com>

* reduce repeated conversions of same url.URL object

Signed-off-by: kim <grufwub@gmail.com>

* move worker.Worker to concurrency subpackage, add WorkQueue type, limit transport http client use by WorkQueue

Signed-off-by: kim <grufwub@gmail.com>

* fix security advisories regarding max outgoing conns, max rsp body size

- implemented by a new httpclient.Client{} that wraps an underlying
  client with a queue to limit connections, and limit reader wrapping
  a response body with a configured maximum size
- update pub.HttpClient args passed around to be this new httpclient.Client{}

Signed-off-by: kim <grufwub@gmail.com>

* add httpclient tests, move ip validation to separate package + change mechanism

Signed-off-by: kim <grufwub@gmail.com>

* fix merge conflicts

Signed-off-by: kim <grufwub@gmail.com>

* use singular mutex in transport rather than separate signer mus

Signed-off-by: kim <grufwub@gmail.com>

* improved useragent string

Signed-off-by: kim <grufwub@gmail.com>

* add note regarding missing test

Signed-off-by: kim <grufwub@gmail.com>

* remove useragent field from transport (instead store in controller)

Signed-off-by: kim <grufwub@gmail.com>

* shutup linter

Signed-off-by: kim <grufwub@gmail.com>

* reset other signing headers on each loop iteration

Signed-off-by: kim <grufwub@gmail.com>

* respect request ctx during retry-backoff sleep period

Signed-off-by: kim <grufwub@gmail.com>

* use external pkg with docs explaining performance "hack"

Signed-off-by: kim <grufwub@gmail.com>

* use http package constants instead of string method literals

Signed-off-by: kim <grufwub@gmail.com>

* add license file headers

Signed-off-by: kim <grufwub@gmail.com>

* update code comment to match new func names

Signed-off-by: kim <grufwub@gmail.com>

* updates to user-agent string

Signed-off-by: kim <grufwub@gmail.com>

* update signed testrig models to fit with new transport logic (instead uses separate signer now)

Signed-off-by: kim <grufwub@gmail.com>

* fuck you linter

Signed-off-by: kim <grufwub@gmail.com>

vendor/codeberg.org/gruf/go-cache/v2/compare.go

@@ -0,0 +1,23 @@
+package cache
+
+import (
+	"reflect"
+)
+
+type Comparable interface {
+	Equal(any) bool
+}
+
+// Compare returns whether 2 values are equal using the Comparable
+// interface, or failing that falls back to use reflect.DeepEqual().
+func Compare(i1, i2 any) bool {
+	c1, ok1 := i1.(Comparable)
+	if ok1 {
+		return c1.Equal(i2)
+	}
+	c2, ok2 := i2.(Comparable)
+	if ok2 {
+		return c2.Equal(i1)
+	}
+	return reflect.DeepEqual(i1, i2)
+}