[syncer] fix syncer timeout

[0xcb9ff9]

Description

• GetBlocks exists duplicate timeout context, remove it
• bulkSyncWithPeer re-select peer

Changes include

• Bugfix (non-breaking change that solves an issue)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the relevant labels

Testing

• I have tested this code with the official test suite

[codecov-commenter]

Codecov Report

Merging #319 (c3e135b) into dev (d7c5a9e) will decrease coverage by 0.02%.
The diff coverage is 58.00%.

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@@            Coverage Diff             @@
##              dev     #319      +/-   ##
==========================================
- Coverage   47.74%   47.72%   -0.02%     
==========================================
  Files         132      132              
  Lines       20125    20102      -23     
==========================================
- Hits         9608     9594      -14     
+ Misses       9684     9676       -8     
+ Partials      833      832       -1     

Impacted Files	Coverage Δ
protocol/client.go	48.61% <ø> (-0.61%)	⬇️
protocol/syncer.go	48.50% <58.00%> (-1.11%)	⬇️

... and 2 files with indirect coverage changes

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[0xcb9ff9]

PR #320 replace this

[DarianShawn]

Could you please give more manual testing on this?
No confident with the changing impact on syncing stability.

[DarianShawn]

LGTM