fix: (web3.js) clear the idle timer whenever the websocket closes

[steveluscher]

Problem

If the websocket closes while there's an active idle timer, the connection can enter a corrupt state as described in solana-labs/solana-web3.js#1106.

Summary of Changes

• Clear the idle timer whenever the websocket connection drops.

Fixes #26665.

[codecov]

Codecov Report

Merging #26734 (c23f9de) into master (ce337e0) will increase coverage by 0.0%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   solana-labs/solana#26734   +/-   ##
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  Coverage    77.4%    77.5%           
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  Files          42       42           
  Lines        2462     2465    +3     
  Branches      351      352    +1     
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+ Hits         1908     1911    +3     
  Misses        424      424           
  Partials      130      130