LB-1628: LB radio 429 fix

[mayhem]

LB-1628 points out that LB Radio is crap at dealing with rate limiting, so this PR ensures that request calls handle 439/503 correctly.

Also, for some queries more than 1,000 items were generated, which caused problems. Truncating to first 1,000 tracks is a sufficient fix for this.

[github-actions]

Test Results

  4 files  ±0    4 suites  ±0   4s ⏱️ ±0s
 50 tests ±0   50 ✅ ±0  0 💤 ±0  0 ❌ ±0 
200 runs  ±0  200 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit d931c4d. ± Comparison against base commit 2f3a152.

[github-actions]

Package	Line Rate	Complexity	Health
.	32%	0	❌
content_resolver	0%	0	❌
content_resolver.formats	6%	0	❌
content_resolver.model	0%	0	❌
external	39%	0	❌
listenbrainz	46%	0	❌
musicbrainz	71%	0	➖
patches	27%	0	❌
patches.lb_radio_classes	0%	0	❌
tools	20%	0	❌
.	32%	0	❌
content_resolver	0%	0	❌
content_resolver.formats	6%	0	❌
content_resolver.model	0%	0	❌
external	39%	0	❌
listenbrainz	46%	0	❌
musicbrainz	71%	0	➖
patches	27%	0	❌
patches.lb_radio_classes	0%	0	❌
tools	20%	0	❌
.	32%	0	❌
content_resolver	0%	0	❌
content_resolver.formats	6%	0	❌
content_resolver.model	0%	0	❌
external	39%	0	❌
listenbrainz	45%	0	❌
musicbrainz	69%	0	➖
patches	27%	0	❌
patches.lb_radio_classes	0%	0	❌
tools	20%	0	❌
.	32%	0	❌
content_resolver	0%	0	❌
content_resolver.formats	6%	0	❌
content_resolver.model	0%	0	❌
external	39%	0	❌
listenbrainz	46%	0	❌
musicbrainz	71%	0	➖
patches	27%	0	❌
patches.lb_radio_classes	0%	0	❌
tools	20%	0	❌
Summary	21% (4174 / 19975)	0	❌