pgsql: Allocate JsonLexContexts on the heap to avoid warnings

Allocate JsonLexContexts on the heap to avoid warnings

The stack allocated JsonLexContexts, in combination with codepaths
using goto, were causing warnings when compiling with LTO enabled
as the optimizer is unable to figure out that is safe.  Rather than
contort the code with workarounds for this simply heap allocate the
structs instead as these are not in any performance critical paths.

Author: Daniel Gustafsson <daniel@yesql.se>
Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/2074634.1744839761@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/994a100b37ad8c2fb8282a9fce91a16b4c832277

Modified Files
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src/interfaces/libpq/fe-auth-oauth.c               | 12 +++++------
.../test_json_parser_incremental.c                 | 23 +++++++++++++---------
2 files changed, 20 insertions(+), 15 deletions(-)