fix(lci pp): fix the null_thread_id bug in the LCI parcelport

[JiakunYan]

send() in the LCI parcelport can call HPX yield(). However, send() can be called outside HPX threads, leading to HPX complaining "null_thread_id".

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ -0.15%	✅ 0.00%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (8b438bf)	397874	336695	84.62%
Head commit (c30e9b1)	195086 (-202788)	164798 (-171897)	84.47% (-0.15%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#6401)	2	0	0.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[JiakunYan]

Changes are overwritten by #6402