chore: support go1.18 and update dependencies (#708)

Here's the squash of the following patches that enable support
for go1.18 and update our dependencies.

This diff WILL need to be backported to the release/3.14 branch.

* chore: use go1.17.8

See https://github.com/ooni/probe/issues/2067

* chore: upgrade to probe-assets@v0.8.0

See https://github.com/ooni/probe/issues/2067.

* chore: update dependencies and enable go1.18

As mentioned in https://github.com/ooni/psiphon/commit/7a0d17ea91f8548dedf32daa07bcc00c1839b5b3,
the tree won't build with `go1.18` unless we say it does.

So, not only here we need to update dependencies but also we
need to explicitly say `go1.18` in the `go.mod`.

This work is part of https://github.com/ooni/probe/issues/2067.

* chore(coverage.yml): run with go1.18

This change will give us a bare minimum confidence that we're
going to build our tree using version 1.18 of golang.

See https://github.com/ooni/probe/issues/2067.

* chore: update user agent used for measuring

See https://github.com/ooni/probe/issues/2067

* chore: run `go generate ./...`

See https://github.com/ooni/probe/issues/2067

* fix(dialer_test.go): make test work with go1.17 and go1.18

1. the original test wanted the dial to fail, so ensure we're not
passing any domain name to exercise dialing not resolving;

2. match the end of the error rather than the whole error string.

Tested locally with both go1.17 and go1.18.

See https://github.com/ooni/probe-cli/pull/708#issuecomment-1096447186

internal/engine/httpheader/useragent.go

@@ -3,8 +3,8 @@ package httpheader
 
 // UserAgent returns the User-Agent header used for measuring.
 func UserAgent() string {
-	// 13.2% as of Jan 24, 2021 according to https://techblog.willshouse.com/2012/01/03/most-common-user-agents/
-	const ua = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36"
+	// 7.6% as of Apr 12, 2022 according to https://techblog.willshouse.com/2012/01/03/most-common-user-agents/
+	const ua = "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:98.0) Gecko/20100101 Firefox/98.0"
 	return ua
 }
 
@@ -12,5 +12,5 @@ func UserAgent() string {
 // pretent to be a command line HTTP client.
 func CLIUserAgent() string {
 	// here we always put the latest version of cURL.
-	return "curl/7.79.1"
+	return "curl/7.82.0"
 }